Effects of hyperlipemia on radioimmunoassays for progesterone, testosterone, thyroxine, and cortisol in serum and plasma samples from dogs

Hyperlipemic serum and plasma samples often are received by clinical laboratories for endocrinologic analysis by radioimmunoassay. We designed a study to determine what effect, if any, hyperlipemia has on estimation of lipid-soluble hormone concentrations determined by solid-phase radioimmunoassays. Progesterone, testosterone, thyroxine, and cortisol concentrations were determined in canine plasma and serum with various degrees of lipemia. Samples of serum, heparinized plasma, and EDTA-treated plasma were obtained from blood collected from 4 female and 4 male Beagles by use of evacuated tubes. To induce hyperlipemia in vitro, IV fat emulsion was diluted in deionized water to produce 0 (water only), 33, 67, or 100% mixtures. Twenty microliters of each mixture then was added to the subsamples of serum and plasma from each dog. Hormone concentrations were determined, using validated radioimmunoassays. Triglyceride concentrations were determined by enzymatic assay. Addition of IV fat emulsion in vitro was an accurate and reproducible means of altering triglyceride concentrations in the samples. Triglyceride concentrations as high as 700 mg/dl had no effect on radioimmunoassays for progesterone, testosterone, and thyroxine in serum, heparinized plasma, or EDTA-treated plasma. Addition of 100% (but not 33 or 67%) fat emulsion reduced the mean cortisol concentration in heparinized plasma by 12% (P less than 0.05). This severe hyperlipemia did not affect quantification of cortisol in serum or EDTA-treated plasma.     

Effects of methods used for blood collection on plasma concentrations of luteinising hormone, testosterone, and cortisol in male dogs.

The effects of two putative stressors relative to the collection of blood, namely the environment of the treatment room and the pain associated with venepuncture, on plasma levels of luteinising hormone (LH), testosterone and cortisol were examined in six trained male experimental dogs. Blood samples were collected from the dogs in a treatment room as well as in the kennels (control), and by venepuncture as well as via an indwelling intravenous catheter (control). No significant influence of either stressor on plasma levels of LH, testosterone or cortisol was found. Plasma concentrations of these hormones varied considerably both between and within dogs. Mean (+/- SEM; n = 6) plasma concentrations were 4.3 +/- 1.0 micrograms/l for LH, 4.6 +/- 1.9 nmol/l for testosterone and 68 +/- 10 nmol/l for cortisol. It was concluded that the putative stressors, the environment of the treatment room and the pain associated with venepuncture, did not significantly influence plasma levels of LH, testosterone or cortisol in trained male experimental dogs. This conclusion implies that under the experimental conditions described, the validity of results will not be affected by the method of blood collection used.     

Comparison of cortisol concentrations in saliva and plasma of dogs

It is increasingly important to have simple, non-invasive indicators of stress in animals. Studies in various species have shown that concentrations of cortisol in saliva relate closely to plasma levels of the free hormone; the aim of the present procedure was to show a similar correlation in the dog. Baseline blood and saliva samples were collected concurrently from six male beagles. Synthetic adrenocorticotrophic hormone was given and further samples were collected at 0.25, 0.5, one, two and 2.5 hours later. The results indicated a statistically significant correlation between the levels of cortisol in blood and saliva. Concentrations in saliva were between 5 and 10 per cent of those in plasma at each collection time. To demonstrate a response to a more natural stimulus, saliva samples were taken from a dog during exposure to a known stressor for that individual. The results showed a marked, delayed increase from baseline which was maintained for at least 0.5 hours after stressing.     

Pfaffia paniculata-induced changes in plasma estradiol-17beta, progesterone and testosterone levels in mice

The present study undertook chemical analysis of components of Pfaffia paniculata roots. In addition, an animal experiment was conducted in which mice had ad libitum access to water enriched with powdered P. paniculata root for 30 days. Changes in plasma concentrations of estradiol-17beta and progesterone in female mice and of testosterone in male mice were ascertained. The results revealed that P. paniculata roots contain two types of phytosteroids, beta-sitosterol and stigmasterol, in addition to other compounds such as pfaffic acid, allantoin, saponins, beta-sitosteryl-beta-D-glucoside, and stigmasteryl-beta-D-glucoside. Regarding changes in plasma concentrations of hormones, levels of the sex hormones estradiol-17beta, progesterone and testosterone were clearly higher for mice that drank P. paniculata root-enriched water than for mice that drank plain water. Powdered P. paniculata root is easily dissolved in feed or water, and as no adverse reactions were seen in mice within 30 days of oral intake, consumption of P. paniculata for long periods of time appears safe.     

Changes in adrenal cortisol secretion as reflected in the urinary cortisol/creatinine ratio in dogs

In Experiment 1, voided urine samples were collected from 12 adult dogs at 0500, 1400, and 2200 hr for 4 days. Cortisol was measured in unextracted urine by radioimmunoassay, creatinine by spectrophotometry, and the cortisol/creatinine ratio (UCCR) was calculated for each sample. There was considerable variation both within and among dogs in UCCR but there was no consistent time of day fluctuation in UCCR. In Experiment 2, these dogs were randomly assigned to 1 of 4 groups. The groups received each of 4 treatments (saline, dexamethasone, ACTH gel, and aqueous ACTH) at 7 day intervals in a Latin square design. All urine was collected from 0 through 8 hr. Blood samples were collected at 20 minute intervals from 0 through 8 hr. Plasma cortisol exposure was determined by quantifying area under the curve (AUC). UCCR measurement was shown to differentiate basal from elevated, but not lowered, cortisol secretion. A positive linear relationship between UCCR and AUC was seen for all treatments except dexamethasone. These results indicate that changes in cortisol secretion are reflected in changes in UCCR, but measurement of UCCR may lack sensitivity to differentiate basal from reduced states of cortisol secretion. In Experiment 3, urine was collected daily before and during induction therapy with o,p′-DDD from dogs with pituitary-dependent hyperadrenocorticism. Successful suppression of the adrenal glands was accompanied by a progressive decrease in UCCR. There was considerable variation in the rate of adrenal suppression.     

Changes in the plasma testosterone level and testicular superoxide dismutase activity of 5 azoospermic beagles after GnRH analogue injections

The peripheral blood plasma testosterone (T) levels and superoxide dismutase (SOD) activity were measured in 5 azoospermic (AZ-) beagles. The mean values in the AZ-dogs were significantly lower than in 7 control beagles (P<0.001). Subcutaneous injections of 1 mug/kg GnRH analogue three times weekly in the AZ-dogs induced significant increases in mean T level and SOD activity (P<0.05) and improvement in spermatogenesis. Thus, spermatogenic function in the dog appears to be maintained by T and normal SOD activity in the testis.     

Correlations among body temperature,plasma progesterone,cortisol and prostaglandin F2alpha of the periparturient bitch

The results of this study suggest that, besides the irrelevant role of body temperature measurement to predict the impending parturition in the bitch, progesterone and 15-ketodihydroprostaglandin F2alpha plasma level records could be more suitable to detect the approaching whelping in this species. More interesting was the statistically significant substantial increase in body temperature beginning 12 h after the onset of parturition. Therefore, if any significant increase in body temperature is recorded at the end of pregnancy without the beginning of the expulsion of fetuses, it could indicate problems at parturition. In this study, cortisol levels increased significantly at the time of delivery and remained high 12 h after the beginning of parturition, decreasing within 36 h after the onset of whelping. 15-ketodihydro-prostaglandin F2alpha levels increased significantly 24 h before parturition and again at the onset of whelping. Progesterone levels decreased significantly, starting 24 h before the onset of whelping and remained low after delivery.     

Changes in concentrations of plasma immunoreactive follicle-stimulating hormone, luteinizing hormone, estradiol-17beta, testosterone, progesterone, and inhibin in heifers from birth to puberty

This study was designed to clarify the characteristics of changes in plasma concentrations of reproductive hormones in heifers from birth to puberty. Weekly or daily hormonal changes were observed in 39 heifers. Daily changes in the concentration of follicle-stimulating hormone (FSH) demonstrated a consistent cycle of hormone changes over a 7- to 8-day period in heifers from approximately 10 days to 9 months old. Weekly changes in reproductive hormones showed that there were three brief periods in heifers between birth and puberty in which dramatic changes occur. The first period was the first week after birth, during which a reciprocal relationship between steroid hormones and gonadotropins was observed. At birth, the concentrations of steroid hormones were higher than those at any other age. These hormone levels rapidly decreased within the first week after birth. Gonadotropin levels, however, increased from birth to 1 week of age. The second period of major change was at approximately 4 weeks of age when there was an increase in the concentrations of luteinizing hormone (LH), estradiol-17beta, testosterone, and immunoreactive inhibin. The third period was the last 5 weeks before the first ovulation, when there was an increase in the concentrations of estradiol-17beta followed by an increase in (LH). These results suggest that regular hormone changes start from 10 days after birth and that the periods from birth to 4 weeks of age and the last 5 weeks before the first ovulation in heifers are important to the development of reproductive functions before puberty.     

Response of plasma cortisol and progesterone after ACTH challenge in ovariectomized lactating dairy cows

Shortened and weakened estrous expressions could be one of the causes of poor heat detection rate. Non-specific acute stresses are assumed to depress expression of estrus by an increase of plasma progesterone which may originate from the adrenal cortex. The objective of the present study was to examine whether the adrenal cortex can secrete significant amounts of progesterone in response to exogenous adrenocorticotropic hormone (ACTH) in lactating cows. Four cows had estrus synchronized and were ovariectomized in the luteal phase. The cows were given 25 IU ACTH through an indwelling catheter 5 h after catheterization. Blood samples were collected at an interval of 30 min. In 3 of the 4 cows, plasma progesterone concentrations increased significantly 0.5-1.5 h after the first ACTH challenge with a mean peak value of 4.2 +/- 0.4 (S.D.) ng/ml. A similar response was also observed after the second ACTH challenge. Peak plasma progesterone concentrations in the 3 cows after first ACTH challenge were comparable with the progesterone values in the luteal phase of each cow. The results suggest that lactating cows have the capability to secrete a significant amount of progesterone from the adrenal cortex.     

Effect of octreotide on plasma concentrations of glucose, insulin, glucagon, growth hormone, and cortisol in healthy dogs and dogs with insulinoma

The inhibitory effect of the somatostatin analogue octreotide on the secretion of insulin could be used in the treatment of insulinoma. However, current information on the effectiveness of octreotide in dogs is conflicting. Therefore, the endocrine effects of a single subcutaneous dose of 50 microg octreotide were studied in healthy dogs in the fasting state (n=7) and in dogs with insulinoma (n=12). Octreotide did not cause any adverse effects. In healthy dogs in the fasting state, both plasma insulin and glucagon concentrations declined significantly. Basal (non-pulse related) GH and ACTH concentrations were not affected. A slight but significant decrease in the plasma glucose concentrations occurred. Dogs with insulinoma had significantly higher baseline insulin concentrations and lower baseline glucose concentrations than healthy dogs in the fasting state. Plasma glucagon, GH, ACTH, and cortisol concentrations did not differ from those in healthy dogs. Baseline plasma insulin concentrations decreased significantly in dogs with insulinoma after octreotide administration, whereas plasma concentrations of glucagon, GH, ACTH, and cortisol did not change. In contrast to the effects in the healthy dogs, in the dogs with insulinoma plasma glucose concentrations increased. Thus, the consistent suppression of plasma insulin concentrations in dogs with insulinoma, in the absence of an suppressive effect on counter-regulatory hormones, suggests that further studies on the effectiveness of slow-release preparations in the long-term medical treatment of dogs with insulinoma are warranted.     

Changes in plasma testosterone levels and semen quality after 3 injections of a GnRH analogue in 3 dogs with spermatogenic dysfunction

Three male Beagles with low plasma luteinizing hormone and testosterone levels and spermatogenic dysfunction (SD-dogs) were given 3 weekly subcutaneous injections of a gonadotropin-releasing hormone analogue (Buserelin; GnRH-AB). The plasma T level of all of the SD-dogs increased and peaked at 4-6 weeks after the first injection. The total number of sperm and the sperm motility of the three SD-dogs increased 5-7 weeks after the first injection. Therefore, the authors concluded that 3 weekly injections of GnRH-AB transiently improves semen quality in some cases of canine spermatogenic dysfunction.     

Influence of dimethoate on testicular and epididymal organs, testosterone plasma level and their tissue residues in rats.

The effect of dimethoate at two dosage levels (6.25 and 12.50 mg/kg b. wt.) on male reproduction tissues and their tissue residues in rats were studied. The tested doses were given orally to male rats for 65 consecutive days. Sex organs weight analysis, semen picture, testosterone levels and histopathology of the male genital organs were the criteria used to evaluate the reproductive efficiency of the treated rats. There was a dose-related decrease in the weights of most genital organs and sperm motility associated with an increase in the percentages of dead and morphologically abnormal spermatozoa of treated rats. A decrease in plasma testosterone levels was observed in the treated groups. Histological examination revealed that dimethoate caused testicular lesions characterized by moderate to severe degenerative changes of spermatogonial cells and by partial arrest of spermatogenesis. Sections from liver revealed that the central veins and hepatic sinusoids appeared dilated, with some areas of haemorrhage. The highest concentrations from dimethoate were found in liver and tests and the lowest in skeletal muscle. Dimethoate and its metabolite analog were still present in a detectable concentration 21 days after stopping its oral administration.     

Blood plasma concentrations of oestradiol-17beta,testosterone and testosterone/oestradiol ratio in dogs with neoplastic and degenerative testicular diseases

Oestradiol-17beta and testosterone blood plasma concentrations were measured in dogs with Leydig-cell tumours (n=20), Sertoli-cell tumours (n=6), seminomas (n=9), unilateral inguinal cryptorchidism (n=7), abdominal cryptorchidism (n=9, one bilateral), degenerate scrotal testicles (n=6, two bilateral), and animals with normal scrotal testicles (n=20). The testosterone/oestradiol ratio (testosterone concentration [ng/mL]x100/oestradiol concentration [pg/mL]) was calculated.A considerably higher oestradiol concentration was found in dogs with Sertoli-cell tumours (29.0, 14.4-48.3 pg/mL; median, minimum-maximum; P=0.0256, Mann-Whitney test) and lower oestradiol levels were found in animals with seminomas (12.0, 3.4-17.6 pg/mL; P=0.0025) compared to the healthy control group (18.0, 8.6-31.5 pg/mL). Testosterone concentration was decreased in dogs with Sertoli-cell tumours (0.08, 0.03-0.77 ng/mL) when compared to the control group (1.95, 0.05-3.70 ng/mL; P=0.0012). Testosterone/oestradiol ratios differed from the control (9.6, 0.58-35.8) only in dogs with Sertoli-cell tumours (0.32, 0.06-2.80; P=0.0005). Clinical signs of feminization were observed in five dogs with Sertoli-cell tumour and one dog with a Leydig-cell tumour, and were more often associated with decreased testosterone/oestradiol ratios than with an increased oestradiol-17beta concentration.