Udder edema in cattle: effects of diuretics (furosemide, hydrochlorothiazide, acetazolamide, and 50% dextrose) on serum and urine electrolytes

Blood and urine chemical values at parturition in clinically normal Holstein cows (n = 12) were compared with the same values in Holstein cows developing udder edema (n = 12). There was no statistically significant mean difference between the 2 groups for the serum and urine chemical data. Furosemide (500 mg) given IV caused a significant increase in serum calcium and sodium, urine chloride, potassium, and sodium, and fractional excretional ratio of chloride, potassium, and sodium. There was a significant mean decrease in the serum potassium, urine creatinine, osmolality, pH, and specific gravity. Hydrochlorothiazide (250 mg) given IV caused a significant mean increase in serum chloride, urine chloride, potassium, and sodium, and fractional excretion ratio of chloride, potassium, and sodium. There was a significant mean decrease in serum potassium and sodium, urine osmolality, pH, and specific gravity. Acetazolamide (500 mg) given IV caused a significant mean increase in blood urea nitrogen, serum chloride and glucose, urine sodium, and fractional excretion ratio of sodium, while causing a significant mean decrease in serum potassium, sodium, and phosphorus, and urine creatinine. Dextrose (500 g) given IV as a 50% solution caused a statistical mean increase in serum glucose, urine chloride, potassium, and sodium, and fractional excretion ratio of chloride and potassium. A statistical mean decrease occurred in the packed cell volume, blood urea nitrogen, serum calcium, potassium, sodium, and phosphorus, urine creatinine, osmolality, and pH.     

Renal effects of carprofen administered to healthy dogs anesthetized with propofol and isoflurane

OBJECTIVE: To evaluate renal effects of carprofen in healthy dogs following general anesthesia. DESIGN: Randomized clinical trial. ANIMALS: 10 English hound dogs (6 females and 4 males). PROCEDURE: Dogs were randomly assigned to control (n = 5) or carprofen (5) groups. Anesthesia was induced with propofol (6 to 8 mg/kg [2.7 to 3.6 mg/lb] of body weight, i.v.) and maintained with isoflurane (end-tidal concentration, 2.0%). Each dog underwent two 60-minute anesthetic episodes with 1 week between episodes, and mean arterial blood pressure was maintained between 60 and 90 mm Hg during each episode. Dogs in the carprofen group received carprofen (2.2 mg/kg [1 mg/lb], p.o.) at 9:00 AM and 6:00 PM the day before and at 7:00 AM the day of the second anesthetic episode. Glomerular filtration rates (GFR) were determined during each anesthetic episode by use of renal scintigraphy. Serum creatinine and BUN concentrations and the urine gamma-glutamyltransferase-to-creatinine concentration (urine GGT:creatinine) ratio were determined daily for 2 days before and 5 days after general anesthesia. RESULTS: Significant differences were not detected in BUN and serum creatinine concentrations, urine GGT:creatinine ratio, and GFR either between or within treatment groups over time. CONCLUSIONS AND CLINICAL RELEVANCE: Carprofen did not significantly alter renal function in healthy dogs anesthetized with propofol and isoflurane. These results suggest that carprofen may be safe to use for preemptive perioperative analgesia, provided that normal cardiorespiratory function is maintained.     

Effect of diet on gentamicin-induced nephrotoxicosis in horses.

Gentamicin sulfate-induced nephrotoxicosis was compared in 2 groups of horses fed different rations. Four horses were fed only alfalfa hay, and 4 other horses were fed only whole oats. Seven days after initiation of the diet, all horses were given gentamicin IV (5 mg/kg of body weight) every 12 hours for 22 days. Urinary gamma-glutamyl-transferase to urinary creatinine (UGGT:UCr) ratio was calculated daily, and serum concentration of gentamicin was measured at 1 and 12 hours after drug administration. Results indicated that horses fed oats had greater renal tubular damage than did horses fed alfalfa. Mean UGGT:UCr for horses fed alfalfa was 47.1 +/- 18.8 and was 100.0 +/- 19.0 for horses fed oats (P = 0.007). The UGGT:UCr in horses fed oats was greater than 100 for a total of 54 days; horses fed alfalfa had UGGT:UCr greater than 100 for only 7 days. Two horses not given gentamicin were fed only oats and 2 were fed only alfalfa. These horses had mean UGGT:UCr of 17.6 +/- 2.2 and 30.5 +/- 3.0, respectively. Mean peak and trough concentrations of gentamicin were statistically different for horses fed oats and those fed alfalfa (peak 23.16 +/- 1.87 and 14.07 +/- 1.79 micrograms/ml, respectively [P = 0.0001], and trough, 1.81 +/- 0.69 and 0.71 +/- 0.70 micrograms/ml, respectively [P = 0.0270]). Mean half-lives of gentamicin (estimated from peak and trough concentrations) for horses fed alfalfa (2.58 +/- 0.26 hours) and horses fed oats (2.88 +/- 0.27 hours) were not significantly different. Horses fed only oats had greater degree of gentamicin-induced nephrotoxicosis than did those fed only alfalfa.     

The Effect of Hetastarch (670/0.75) on Urine Specific Gravity and Osmolality in the Dog

Background: Urine specific gravity (USG) is used clinically to estimate urine osmolality (UOsm). Although USG has been shown to have a linear correlation with UOsm in dogs, the relationship is altered when there are significant numbers of high molecular weight (MW) molecules in the urine.
Hypothesis: USG would no longer predict UOsm in dogs given intravenous hetastarch (670/0.75)(HES).
Animals: Eight healthy employee-owned adult dogs.
Methods: Prospective, controlled experimental study. USG and UOsm were measured every 30 minutes from t=0 minutes to t=360 minutes. Dogs were administered 20mL/kg of either NaCl 0.9% (control group, n=4) or HES (treatment group, n=8) IV over 1 hour starting at t=90 minutes.
Results: There was a decrease in UOsm in both groups starting at t=120 minutes and continuing for the study duration, and there was no significant difference in UOsm between treatment and control groups across all time points. There was an appropriate decrease in USG from t=120 minutes for the control group. In the treatment group, USG increased significantly at t=120 minutes ( P = .0006), t=150 minutes ( P = .0002), and t=180 minutes ( P = .0044). The largest increase in USG occurred at t=150 minutes with a mean USG of 1.070 ± 0.021 (range 1.038-1.104).
Conclusions and clinical importance: Urine specific gravity should not be used to estimate urine solute concentration in dogs following the administration of 20mL/kg of HES. In a clinical setting, the evaluation of USG following this dose of HES may lead to an overestimation of urine concentration.     

Diuretic effects of fenoldopam in healthy cats

Objective: To determine the effect of fenoldopam infusion on urine output, sodium excretion, creatinine clearance, and indirect blood pressure in healthy cats. Design: Prospective study. Setting: Veterinary medical teaching hospital. Animals: Eight purpose‐bred cats, 2–4 years old. Interventions: None. Measurements: Urine output was measured hourly for 12 hours before and after fenoldopam administration. Sodium excretion, modified creatinine clearance, and fractional sodium excretion were measured before and following fenoldopam administration. Urine specific gravity, central venous pressure, and systolic blood pressure were measured every 4 hours during the experiment. Main results: Compared with pre‐infusion values, urine output, sodium excretion, and fractional excretion of sodium increased significantly 6 hours after initiation of fenoldopam infusion. This increase was sustained throughout the observation period. The modified creatinine clearance decreased significantly following 2 hours of fenoldopam infusion, but increased significantly by 6 hours after infusion, the time of peak urine output. Changes in urine specific gravity mirrored changes in fractional sodium excretion, whereas the central venous pressure mirrored changes in modified creatinine clearance. The diuretic effect in cats was prevented when a dopamine receptor blocking agent was administered before fenoldopam infusion. Conclusion: Fenoldopam at a dose of 0.5 μg/kg/min induces diuresis in cats in a delayed manner. This increase appears to be due, in part, to dopamine receptor‐induced natriuresis. Changes in glomerular filtration rate may also occur.     

An updated review: Laboratory investigation of equine renal disease

A variety of laboratory tests are available to assist the clinician in the assessment of kidney health and function. The majority of widely used tests are indicative of altered renal function, not becoming abnormal until function is significantly compromised. These include serum urea and creatinine concentrations, serum electrolyte concentrations, urine specific gravity (USG), fractional electrolyte excretion ratios and symmetric dimethylarginine (SDMA) concentrations. Some of these parameters may also be affected by nonrenal disease. The results of a further group of tests can indicate renal damage, but do not reflect renal function. These include urine tubular enzyme concentrations, urine protein concentrations, urine neutrophil gelatinase-associated lipocalin (NGAL) concentrations and cytological abnormalities.     

CHANGES IN RENAL FNCTION IN CATS FOLLOWING TREAMENT OF HYPERTHYROIDISM USING131I

Changes in renal fnction of twenty-two cats treated for hyperthyrodism using radioiodine were evaluated. Serum thyroxine (T₄), serum creatinine, blood urea nitrogen (BUN) and urine specificgravity were measured before treatment and 6 and 30 days after treatment. Twenty-two cats had pretreatment and 21 cats had 6 day posttreatment measurement of glomercular filtration rate (GFR) using nuclear medicine imaging techniques. there were significant declines in serum T₄ at 6 days following treatment, but the changes in GFR, serum creatinine and BUN were not significant. At 30 days following treatment, there were significant increases in BUN and serum creatinine and further significant declines in serum T₄. Nine cats were in renal failure prior to treatment and 13 cats were in renal failure 30 days following treatment. Renal failure was defined as BUN greater than 30 mg/dl and/or serum creatinine greater than 1.8 mg/dl with concurrent urine specific gravity less than 1.035. these 13 cats included eight of 9 cats in renal failure prior to treatment on 9 of these 13 cats indicated that all remained in renal failure. Based on receiver operating curve analysis of pretreatment glomerular filtration rate (GFR) in predicting posttreatment renal failure, a value of 2.25 ml/kg/min as a point of maximum sensitivity (100%) and spefificity (78%) was derived, Fifteen of 22 cats had pretratmentGFR measurements of less than 2.25 ml/kg/min. these 15 cats included all 9 cats in renal failure and 65 cats with normal renal clinicopathologic values prior to treatment. at 30 days following treatment, 13 of these 15 cats were in renal failure. The 2 cats not in renal failure had persistently increased serum T₄ values. seven of 22 cats had pretreatment GFR measurements greater than 225 ml/kg/min. None of these 7 cats was in renal failure at 30 days following treatment, all cats having normal BUN, serum creatinine, and urine specific gravity values. It was concluded that significant declines in renal function occur after treatment of hyperthyroidism and this decline is clinically important in cats with renal disease. Pretreatment measurement of GFR is valuable in detecting subclinical renal disease and in predicting which cats may have clinically important declines in renal function following treatment.     

Quantitative urinalysis in kittens from four to thirty weeks after birth.

To evaluate renal function and obtain reference values for measurements of urinary excretion of various substances, quantitative urinalysis was performed in healthy, growing kittens from 4 to 30 weeks after birth. Endogenous creatinine clearance, 24-hour urine protein excretion, and urine protein-to-creatinine ratio were determined. Additionally, fractional excretion to creatinine clearance was calculated for calcium, inorganic phosphorus, sodium, potassium, and chloride. Mean +/- SD endogenous creatinine clearance values (range, 3.80 +/- 0.48 to 4.74 +/- 0.61 ml/min/kg) were significantly (P less than 0.0001) higher in kittens 9 to 19 weeks old, compared with younger (range, 1.39 +/- 0.85 to 3.59 +/- 0.86 ml/min/kg) and older kittens (range, 2.69 +/- 0.40 to 3.46 +/- 0.37 ml/min/kg). Mean values for all kittens for 24-hour urine protein excretion (range, 2.54 +/- 1.81 mg/kg at 4 weeks to 11.39 +/- 7.61 mg/kg at 14 weeks) and for urine protein-to-creatinine ratio (range, 0.14 +/- 0.03 to 0.34 +/- 0.18) varied from week to week of age. The urine protein-to-creatinine ratio in kittens greater than or equal to 9 weeks old correlated well (R2 = 0.861) with 24-hour urine protein excretion. Urinary fractional excretion of calcium, inorganic phosphorus, sodium, potassium, and chloride in kittens varied among age groups, being significantly (P less than 0.01) different for potassium and calcium in young kittens (4 to 6 weeks) and older kittens (greater than or equal to 7 weeks).     

Magnesium status and the effect of magnesium supplementation in feline hypertrophic cardiomyopathy.

Magnesium deficiency has been associated with the development of cardiovascular disease in several species. Cats may be predisposed to alterations in magnesium status because of recent changes in the composition of commercial feline diets. The purposes of this study were 1) to examine the dietary history of cats with hypertrophic cardiomyopathy (HCM), 2) to study magnesium status of cats with HCM compared to normal cats, and 3) to determine the effects of magnesium supplementation in cats with HCM. In part 1 of the study, diets of 65 cats with HCM were examined retrospectively. Forty of the 45 cats for which diets could be determined (89%) ate a diet designed to be magnesium-restricted and/or to produce an acidic urine. In part 2 of the study, 10 cats with HCM were compared to 10 healthy control cats for serum creatinine and magnesium; urine creatinine and magnesium, urine specific gravity and pH, and fractional excretion of magnesium. Urine creatinine and specific gravity were higher in control cats than in cats with HCM. No other differences were found between the 2 groups. In part 3, cats with HCM were supplemented with either 210 mg magnesium chloride (n = 15) or 210 mg lactose (n = 15) for 12 wk. No differences between the 2 groups were found for changes in either magnesium status or echocardiographic parameters. However, the 30 cats with HCM, as a group, did show significant improvements in measures of cardiac hypertrophy over the 12-week period. This was likely the result of treatment with other medications, rather than the magnesium supplementation. The results of this study suggest that cats with HCM are likely to be fed magnesium-restricted diets, but that they do not appear to have altered magnesium status compared to healthy controls.     

Renal reabsorption of magnesium and calcium by cattle with renal tubular dysplasia

The concentrations of magnesium and calcium in the serum and urine and their rates of clearance were determined in cattle with renal tubular dysplasia, an autosomal recessive hereditary disease associated with a deletion of the paracellin-1 gene in Japanese Black cattle. There were no significant differences in the serum or urine magnesium concentrations between normal cattle and cattle which were heterozygous or homozygous for the condition. Serum calcium concentrations tended to be lower in the homozygous cattle, and the serum creatinine and urea nitrogen concentrations were significantly higher in the homozygous cattle. The ratio of magnesium:creatinine and the fractional excretion of magnesium were higher in cattle with the disease than in normal cattle. There were no significant differences in urine calcium concentration, the calcium:creatinine ratio, and fractional excretion of calcium between normal cattle and cattle which were homozygous or heterozygous for the condition. The creatinine clearance was significantly lower in the homozygous cattle than in normal cattle. The clearance, excretion rate, reabsorption rate and reabsorption rate:clearance ratio of magnesium in cattle with renal tubular dysplasia were significantly lower than in normal cattle. The clearance rate and reabsorption rate of calcium were also significantly lower in the affected cattle, but the excretion rate and reabsorption rate:clearance of calcium were not different between the normal cattle and the cattle homozygous for the condition. In cattle with the condition the rate of reabsorption of magnesium by the kidneys was low, but the rate of reabsorption of calcium was normal.     

Effects of general anesthesia and surgery on renal function in healthy dogs

OBJECTIVES: To evaluate renal function in healthy dogs undergoing general anesthesia and ovariohysterectomy without concurrent IV administration of fluids. ANIMALS: 35 healthy client-owned dogs. PROCEDURE: Dogs were medicated with promazine hydrochloride (0.05 mg/kg of body weight, SC) approximately 45 minutes before induction of anesthesia with thiopental sodium (10 to 15 mg/kg, IV). Anesthesia was maintained with 2% halothane in oxygen. Ovariohysterectomies were performed by senior veterinary students under the direct supervision of a veterinary surgeon. Renal function was assessed (serum urea and creatinine concentrations, fractional clearance of sodium, urine alkaline phosphatase [ALP] and gamma-glutamyltransferase [GGT] activities, urine specific gravity, and enumeration of renal tubular epithelial cells in urine sediment) prior to and 24 and 48 hours after surgery. RESULTS: Duration of general anesthesia ranged from 80 to 310 minutes. Urine specific gravity and ALP activity and serum urea and creatinine concentrations did not change over time. Fractional clearance of sodium decreased 24 and 48 hours after surgery, whereas urine GGT activity and the ratio of urine GGT activity to urine creatinine concentration increased 24 hours after surgery, compared with presurgery values. Renal tubular epithelial cells increased in number in urine sediment from 11 of 35 (31.4%) dogs and 5 of 35 (14.3%) dogs 24 and 48 hours after surgery, respectively. However, this increase was not clinically relevant. CONCLUSIONS AND CLINICAL RELEVANCE: Intravenous administration of fluids to healthy dogs undergoing general anesthesia and elective surgery may not be necessary for maintenance of renal homeostasis.     

Acute intrinsic renal failure in cats: 32 cases (1997-2004)

OBJECTIVE: To determine patient demographics, clinicopathologic findings, and outcome associated with naturally acquired acute intrinsic renal failure (ARF) in cats. DESIGN: Retrospective case series. ANIMALS: 32 cats with ARF. PROCEDURES: Cats were considered to have ARF if they had acute onset of clinical signs (< 7 days), serum creatinine concentration > 2.5 mg/dL (reference range, 0.8 to 2.3 mg/dL) and BUN > 35 mg/dL (reference range, 15 to 34 mg/dL) in conjunction with urine specific gravity < 1.025 or with anuria or increasing serum creatinine concentration despite fluid therapy and normal hydration status, and no signs of chronic renal disease. Cases were excluded if cats had renal calculi or renal neoplasia. RESULTS: Causes of ARF included nephrotoxins (n = 18 cats), ischemia (4), and other causes (10). Eighteen cats were oliguric. For each unit (mEq/L) increase in initial potassium concentration, there was a 57% decrease in chance of survival. Low serum albumin or bicarbonate concentration at initial diagnosis was a negative prognostic indicator for survival. Initial concentrations of BUN, serum creatinine, and other variables were not prognostic. Seventeen (53%) cats survived, of which 8 cats had resolution of azotemia and 9 cats were discharged from the hospital with persistent azotemia. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that survival rates of cats with ARF were similar to survival rates in dogs and that residual renal damage persisted in approximately half of cats surviving the initial hospitalization.     

Urine sulfated and nonsulfated bile acids as a diagnostic test for liver disease in cats

Urine bile acid (UBA) tests reflecting "average" serum bile acid (SBA) concentrations may have greater practical utility than paired SBA samples in cats. This study evaluated whether urine sulfated bile acids (USBAs), urine nousulfated bile acids (UNSBAs), or a combined approach had a clinical utility equivalent to SBAs. Routine serum biochemistry tests, SBA concentrations, and urine samples were collected from 54 cats with hepatobiliary disease, 17 cats with nonhepatic disorders, and 8 healthy cats. UBAs were measured by a quantitative enzymatic colorimetric method, and results were normalized with urine creatinine (UCr) concentrations. Significantly higher values occurred in cats with liver disease than in cats without liver disease for USBA : UCr, UNSBA:UCr, and (USBA and UNSBA) : UCr, P < .05 each. UBA tests with diagnostic performance (sensitivity [SS], specificity [SP], and positive and negative predictive values [PV+ and PV-]) equivalent to SBAs were the UNSBA : UCr and the combined test (SS: 87, 87 versus 85; SP: 88, 88 versus 88; PV+: 96, 96 versus 96; PV-: 68, 65 versus 68; UNSBA : UCr, [USBA, and UNSBA]: UCr versus SBA, respectively). Clinical applications of the UNSBA : UCr or the combined (USBA and UNSBA) : UCr test should be useful as convenient diagnostic tests for identifying cats with liver disease and high SEA concentrations.     

Estimation of Quantitative Enzymuria in Dogs With Gentamicin-Induced Nephrotoxicosis Using Urine Enzyme/Creatinine Ratios From Spot Urine Samples

The correlation between 24-hour urinary excretion of N -acetyl-β- d -glucosaminidase (NAG) and γ-glutamyl transferase (GGT) with urine NAG and GGT/creatinine ratios was assessed in dogs with gentamicin-induced nephrotoxicosis. Eighteen 6-month-oid male Beagles with normal renal function were randomly divided into 3 groups of 6. Each group was fed a different concentration of protein (high protein, 27.3%; medium protein, 13.7%; and low protein, 9.4%) for 21 days. After dietary conditioning, gentamicin was administered at a dose of 10 mg/kg IM tid for 8 days and each group was continued on its respective diet. Endogenous creatinine clearance and 24-hour urinary excretion of NAG and GGT were determined after dietary conditioning (day 0) and on days 2, 4, 6, and 8 of gentamicin administration. In addition, urine NAG and GGT/creatinine ratios (IU/L ± mg/dL) were determined from catheterized spot urine samples obtained between 7 and 10 am on the same days. The correlation between 24-hour urinary enzyme excretion and urine enzyme/creatinine ratio in the spot urine samples was evaluated by simple linear regression analysis. Spot sample urine enzyme/creatinine ratios were significantly correlated with 24-hour urinary enzyme excretion through day 4 for dogs on low dietary protein, through day 6 for those on medium protein, and through day 8 for those on high dietary protein. Mean ± SD baseline values for urine NAG/creatinine ratio and 24-hour urinary NAG excretion were 0.06 ± 0.04 and 0.19 ± 0.14 IU/kg/24 hr, respectively. Baseline values for urine GGT/creatinine ratio and 24-hour urinary GGT excretion were 0.39 ± 0.18 and 1.42 ± 0.82 IU/kg/24 hr, respectively.     

Nitric oxide metabolites in naturally occurring canine babesiosis.

Babesiosis, caused by the virulent haemoprotozoan parasite Babesia canis rossi, is an important disease of dogs in South Africa. The nitric oxide metabolites, nitrate and nitrite (collectively termed reactive nitrogen intermediates or RNIs) were measured in admission sera from dogs in a babesiosis-endemic area. Five groups were prospectively studied: mild uncomplicated (n=9), severe uncomplicated (severe anaemia) (n=10) and complicated babesiosis (n=11); and two groups of healthy aparasitaemic dogs: endemic controls from the study area (n=10) and experimental dogs kept in tick-free conditions (n=10). Four measures of RNI production were studied: (i) serum RNI; (ii) serum RNI/creatinine ratio; (iii) fractional clearance of RNI (FC(RNI)); (iv) fractional excretion of RNI (FE(RNI)). Marked elevations of serum RNI occurred in only two dogs, both in the severe uncomplicated group. The highest concentration (log value 5.29 micromol/l) was in a dog that died, but concentrations in the other four dogs that died were unremarkable (0, 0.34, 1.66 and 2.64 micromol/l). Age, appetite and free serum haemoglobin were significant covariates for measures of RNI production. There were no significant differences among the babesiosis groups for serum RNI. Adjustment for creatinine had minor effects on the results. All babesiosis groups had significantly higher serum RNI and RNI/creatinine than the tick-free control group, but did not differ from the endemic controls except for the severe uncomplicated group, which had higher RNI/creatinine. The complicated group had significantly lower FC(RNI) and FE(RNI) than all other groups, except for the tick-free control group, which had similar FE(RNI). The results indicate that, in an endemic area, measures of RNI production are unlikely to be useful indicators of severity or outcome in canine babesiosis.     

Retention of a functional corpus luteum and peripheral concentrations of 13,14-dihydro-15-keto-prostaglandin F2alpha following metestrus administration of Syncro-Mate-B.

This study was conducted to examine the effects of metestrus administration of SyncroMate-B (SMB) on PGF2alpha secretion and corpus luteum (CL) development. In a study replicated over 2 yr, cows were observed for spontaneous estrus in yr 1, and cows received an injection of 25 mg of PGF2alpha and were observed for subsequent estrus in yr 2. At standing estrus (estrus = d 1), cows were randomly allotted to receive either the standard SMB regimen (n = 40) on d 3 of the estrous cycle or no treatment (n = 8). Fifty percent (n = 20) of SMB-treated cows were administered PGF2alpha on d 10 of the estrous cycle 48 h prior to implant removal. Twice-daily blood samples were collected in the morning (AM) and evening (PM) from d 2 AM through d 14 AM of the treated estrous cycle and subsequently analyzed for progesterone (P4) and PGF2alpha metabolite (PGFM). Prior to statistical analysis, SMB- and SMB/PGF2alpha-treated cows were sorted according to P4 concentration at d 10 of the treated estrous cycle to either a CL functional group (P4 > or = 1 ng/mL; n = 20) or a CL nonfunctional group (P4 < 1 ng/mL; n = 17). Following d 10 AM administration of PGF2alpha, functional and nonfunctional groups were further subdivided based on treatment. The groups were as follows: untreated control cows (n = 8); SMB-treated cows retaining a functional CL (SMB-F; n = 8); SMB-treated cows with a nonfunctional CL (SMB-N; n = 11); SMB/PGF2alpha-treated cows retaining a functional CL (SMB/PG-F; n = 12); and SMB/PGF2alpha-treated cows with a nonfunctional CL (SMB/PG-N; n = 6). Of all SMB-treated cows, 54% retained a functional CL through d 10 AM of the treated estrous cycle. Mean serum P4 concentrations increased for cows in all groups until d 7, after which P4 concentrations increased for cows in SMB/PG-F, SMB-F, and control groups and decreased for cows in SMB/PG-N and SMB-N groups. Following PGF2alpha administration on d 10, mean serum P4 concentrations remained < 1 ng/mL for cows in SMB/PG-N and SMB-N groups, decreased to < 1 ng/mL for cows in the SMB/ PG-F group, and remained > 1 ng/mL for cows in SMB-F and control groups. Mean serum PGFM concentrations tended (P = .06) to increase in cows with nonfunctional CL compared with control cows on d 8 AM and were greater (P < .05) in cows with functional CL on d 8 PM through d 9 PM. These results indicate that retention of a functional rather than a nonfunctional CL following metestrus administration of SMB is dependent on a premature release of uterine PGF2alpha.     

Effect of magnesium-deficient diet on serum and urine magnesium concentrations in healthy cats.

OBJECTIVE: To evaluate the efficacy of using serum total and ionized magnesium (Mg) concentrations and urine Mg concentrations to identify Mg deficiency in cats. ANIMALS: 6 healthy castrated male cats. PROCEDURE: A Mg-replete diet was fed for 37 days, followed by a Mg-deficient diet for 37 days. On days 1, 3, and 7 of the last week of each diet, serum ionized and total Mg concentrations were determined; in addition, urine Mg concentration was determined each day of the last week. Serum total and ionized Mg concentrations were compared with urine Mg concentration, amount of Mg excreted during 24 hours (24-hour urine Mg excretion), ratio of urine Mg concentration to urine creatinine concentration (Umg:Ucr), and urinary fractional excretion of Mg (FEmg) to determine which variable best predicted Mg status. RESULTS: Cats fed Mg-deficient diets had significantly lower serum total and ionized Mg concentrations and 24-hour urine Mg excretion values, compared with cats fed Mg-replete diets. Serum total Mg concentration was the best predictor of Mg status. Twenty-four-hour urine Mg excretion was a repeatable, reliable measurement and had the best correlation with serum total Mg concentration. Serum total Mg concentration also correlated with urine Mg concentration, Umg:Ucr, and FEmg. CONCLUSIONS AND CLINICAL RELEVANCE: Serum total and ionized Mg concentrations can be used to identify cats with dietary-induced Mg deficiencies. Twenty-four-hour urine Mg excretion and urine Mg concentration correlated best with serum total Mg concentration and, therefore, may be the most useful urine variables for identifying Mg deficiency.     

Effects of oral administration of furosemide and torsemide in healthy dogs

OBJECTIVE: To investigate the diuretic effects, tolerability, and adverse effects of furosemide and torsemide after short- and long-term administration in healthy dogs. ANIMALS: 8 mixed-breed dogs. PROCEDURES: In a crossover study, furosemide (2 mg/kg), torsemide (0.2 mg/kg), or placebo (bifidobacterium [1 mg/kg]) was administered orally to each dog every 12 hours for 14 days. Blood and urine samples were collected before the study (baseline data) and at intervals on the 1st (short-term administration) and 14th day (long-term administration) of treatment for assessment of urine volume and specific gravity and selected clinicopathologic variables including BUN, creatinine, and aldosterone concentrations, and creatinine clearance. RESULTS: Compared with the baseline value, short-term administration of furosemide or torsemide immediately increased urine volume significantly; after long-term administration of either drug, urine specific gravity decreased significantly. Compared with the effect of placebo, the 24-hour urine volume was significantly increased after short-term administra-tion of furosemide or torsemide. In addition, it was significantly increased after long-term administration of torsemide, compared with that of short-term administration. Long-term administration of furosemide or torsemide increased the BUN and plasma creatinine con-centrations, compared with the baseline value. Compared with the baseline value, plasma aldosterone concentration was significantly increased after long-term administration of either drug and was significantly higher after torsemide treatment than after furosemide treatment. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs, diuretic resistance developed after 14 days of furosemide, but not torsemide, administration; however, both loop diuretics were associated with increased BUN and plasma creatinine concentrations, compared with values before treatment.     

Urinary indices of renal function in sheep with induced aminoglycoside nephrotoxicosis

Aminoglycoside nephrotoxicosis (AGNT) was induced in ewes by daily SC administration of gentamicin. Changes in urinary indices of renal function during the development of AGNT are reported. Measurements from timed, volume-measured urine samples were made on days 0, 7, and 8 and included creatinine clearance, total excretion (TE) rates of electrolytes (Na, K, Cl, P) and urine volume. Measurements from free-catch urine samples (without volume measurement) were made daily and included fractional excretion (FE) rate of electrolytes, urine osmolality, and urine-to-serum osmolality and urine-to-serum creatinine ratios. With the onset of AGNT, FE rates of Na, K, Cl, and P- increased many fold above baseline values (200x, 4 to 5x, 6 to 9x, and 70 to 95x, respectively, on days 7 and 8), indicating decreased tubular reabsorption or increased tubular secretion. The increased FE rates were not representative of increases in total electrolyte excretion rates. The total excretion of Na (TENa) was mildly increased, TEK was decreased, TECl was unchanged, and TEP was significantly increased on days 7 and 8. Abnormal urinalysis results, glucosuria, and increased FEP preceded appreciable increase in serum creatinine concentration. Other abnormal urinary indices of renal function coincided with or followed the increase in serum creatinine concentration. Urinary indices may help characterize renal function associated with the disease state, but did not provide early indication of AGNT.     

Urinary gamma-glutamyl transpeptidase activity in dogs with gentamicin-induced nephrotoxicity

Serum creatinine concentrations, 24-hour endogenous creatinine clearance, and 24-hour urinary gamma-glutamyl transpeptidase (UGGT) activity were measured daily in 6 dogs given nephrotoxic dosages of gentamicin (10 mg/kg of body weight) every 8 hours for 10 days. Mean UGGT activity was significantly increased by day 5 (P less than 0.05) and preceded significant increases in serum creatinine values (greater than 2.0 mg/dl) observed on day 9. Endogenous creatinine clearance remained within normal limits (2.98 +/- 0.96 ml/min/kg) until day 8. Urinalyses performed 8 days after initiation of gentamicin treatment indicated renal tubular damage (granular casts) in 1 of the 6 dogs, and glucosuria in 3 of the 6 dogs. Measurement of UGGT activity was a more sensitive and reliable method of assessing acute renal tubular damage induced by gentamicin than were serum creatinine concentrations or 24-hour endogenous creatinine clearance.