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.     

EFFECT OF STRESS ON STEROID HORMONE LEVELS IN RACEHORSES

SUMMARY Cortisol and testosterone were measured by radioimmunoassay in plasma samples from race horses. None of 6 stressed male horses had Iow cortisol levels but testosterone levels (0.81 ± 0.15 nmol/l) were significantly lower than in healthy horses (1.86 ± 0.31 nmol/l). The conclusion was made that adrenocortical insufficiency is not a common association of stress in race horses. The reduction in testosterone levels is probably a nonspecific response similar to that seen in other species.     

The function of the pituitary-testicular axis in dogs prior to and following surgical or chemical castration with the GnRH-agonist deslorelin

Chemical castration, that is the reduction of circulating testosterone concentrations to castrate levels by administration of a GnRH-agonist implant, is a popular alternative to surgical castration in male dogs. Detailed information concerning the pituitary-testicular axis following administration of a GnRH-agonist implant is still scarce. Therefore, GnRH-stimulation tests were performed in male dogs, prior to and after surgical and chemical castration. This approach also allowed us to determine plasma concentrations of testosterone and oestradiol in intact male dogs for future reference and to directly compare the effects of surgical and chemical castration on the pituitary-testicular axis. In intact male dogs (n = 42) of different breeds GnRH administration induced increased plasma LH, FSH, oestradiol and testosterone concentrations. After surgical castration basal and GnRH-induced plasma FSH and LH concentrations increased pronouncedly. Additionally, basal and GnRH-induced plasma oestradiol and testosterone concentrations decreased after surgical castration. After chemical castration, with a slow-release implant containing the GnRH-agonist deslorelin, plasma LH and FSH concentrations were lower than prior to castration and lower compared with the same interval after surgical castration. Consequently, plasma oestradiol and testosterone concentrations were lowered to values similar to those after surgical castration. GnRH administration to the chemically castrated male dogs induced a significant increase in the plasma concentrations of LH, but not of FSH. In conclusion, after administration of the deslorelin implant, the plasma concentrations of oestradiol and testosterone did not differ significantly from the surgically castrated animals. After GnRH-stimulation, none of the dogs went to pre-treatment testosterone levels. However, at the moment of assessment at 4,4 months (mean 133 days ± SEM 4 days), the pituitary gonadotrophs were responsive to GnRH in implanted dogs. The increase of LH, but not of FSH, following GnRH administration indicates a differential regulation of the release of these gonadotrophins, which needs to be considered when GnRH-stimulation tests are performed in implanted dogs.     

Clinical pharmacology of methadone in dogs

ObjectiveTo investigate the pharmacokinetics and effects of methadone on behaviour and plasma concentrations of cortisol and vasopressin in healthy dogs.Study designRandomized, cross-over, experimental trial.AnimalsNine adult dogs (beagle and beagle cross breeds), four males and five females.MethodsMethadone hydrochloride, 0.4 mg kg^?1, was administered intravenously (IV) and subcutaneously (SC) with a crossover design. Drug and hormone analyses in plasma were performed using Liquid Chromatography–Electrospray Ionization–Tandem Mass Spectrometry and radioimmunoassay respectively. Behavioural data were collected using a standardized protocol.ResultsAfter IV administration, the plasma concentration of methadone at 10 minutes was 82.1 ± 9.2 ng mL^?1 (mean ± SD), the terminal half-life was 3.9 ± 1.0 hours, the volume of distribution 9.2 ± 3.3 L kg^?1 and plasma clearance 27.9 ± 7.6 mL minute^?1 kg^?1. After SC administration, time to maximal plasma concentration was 1.26 ± 1.04 hours and maximal plasma concentration of methadone was 23.9 ± 14.4 ng mL^?1, the terminal half-life was 10.7 ± 4.3 hours and bioavailability was 79 ± 22%. Concentrations of both cortisol and vasopressin were increased for an hour following IV methadone. The observed behavioural effects of methadone were decreased licking and swallowing and an increase in whining after SC administration. The latter finding is notable as it can be misinterpreted as pain when methadone is used as an analgesic.Conclusion and clinical relevanceWhen methadone was administered by the SC route, the half-life was longer, but the individual variation in plasma concentrations was greater compared with IV administration. Increased frequency of whining occurred after administration of methadone and may be a drug effect and not a sign of pain. Cortisol and vasopressin concentrations in plasma may not be suitable for evaluating analgesia after methadone treatment.     

Salivary Cortisol Concentrations in Healthy Dogs and Dogs with Hypercortisolism

Background: Measurement of salivary cortisol is a useful diagnostic test for hypercortisolism (HC) in humans. Objectives: To determine whether measurement of salivary cortisol concentration is a practical alternative to plasma cortisol to diagnose HC, to validate the use of salivary cortisol, and to examine the effect of time of day and sampling location on salivary cortisol. Animals: Thirty healthy dogs and 6 dogs with HC. Methods: Prospective, observational clinical trial including healthy volunteer dogs and dogs newly diagnosed with HC. Salivary and plasma cortisol concentrations were measured with an immunoassay analyzer. Intra‐ and interassay variability, linearity, and correlation between salivary and plasma cortisol concentrations were determined. Results: The required 300 μL of saliva could not be obtained in 88/326 samples from healthy dogs and in 15/30 samples from dogs with HC. The intra‐assay variability for measurement of salivary cortisol was 5–17.7%, the interassay variability 8.5 and 17.3%, and the observed to expected ratio 89–125%. The correlation (r) between salivary and plasma cortisol was 0.98. The time of day and location of collection did not affect salivary cortisol concentrations. Dogs with HC had significantly higher salivary cortisol values than healthy dogs (10.2 ± 7.3 nmol/L versus 1.54 ± 0.97 nmol/L; P < .001). Conclusions and Clinical Importance: The ROCHE Elecsys immunoassay analyzer correctly measured salivary cortisol in dogs. However, a broad clinical application of the method seems limited, because of the large sample volume required.     

Dose–Response Studies for Pituitary and Testicular Function in Male Dogs Treated with the GnRH Superagonist, Deslorelin

We tested the effect of dose of GnRH superagonist on pituitary and testicular function in a study with four groups of four male dogs. The Controls received blank implants and the other three groups received implants containing 3, 6 or 12 mg deslorelin (d ‐Trp⁶‐Pro⁹‐des‐Gly¹⁰‐GnRH ethylamide). In all deslorelin‐treated groups, there was initially an acute increase in plasma concentrations of LH and testosterone, followed by declines such that both hormones became undetectable after approximately 12 days. There was a dose–response in some of these early aspects of the hormone profiles. With respect to long‐term effects of treatment, the 12‐mg dose had significantly greater effects than the smaller doses for the duration of minimum testicular volume [366 ± 77, mean ± SEM (3 mg), 472 ± 74 (6 mg), and 634 ± 59 (12 mg) days], absence of ejaculate [416 ± 88 (3 mg), 476 ± 83 (6 mg), and 644 ± 67 (12 mg) days], undetectable plasma concentrations of LH and testosterone [367 ± 64 (3 mg), 419 ± 72 (6 mg), and 607 ± 69 (12 mg) days], the delay until complete recovery of LH and testosterone secretion [394 ± 65 (3 mg), 484 ± 72 (6 mg) and 668 ± 47 (12 mg) days], and the delay until testes had regrown to normal volume [408 ± 77 (3 mg), 514 ± 74 (6 mg), 676 ± 59 (12 mg) days]. The time taken to restore full ejaculates was also longest for the 12‐mg dose: 716 ± 67 (12 mg) days vs 440 ± 66 (3 mg) and 538 ± 83 (6 mg) days after implantation. There was no correlation between delay to recovery of normal ejaculate quality and body mass. We conclude that the dose–response relationship with deslorelin implants is not expressed with respect to the degree of suppression of reproduction, but on the maximum duration of suppression and thus to delay until recovery.     

Salivary cortisol as a stress parameter in piglets]

The relationship between salivary and plasma levels of total and free cortisol was monitored in 97 male piglets, aged two to four weeks, subjected to castration. Samples were taken 10 minutes before (basal value) as well as one, two, three, four and 24 hours post castration and at the same time intervals from a control group of 17 animals which did not undergo surgery. Simultaneously to blood (indwelling catheter) withdrawing saliva was collected by two cotton swabs. Cortisol levels were measured by radioimmunoassay (RIA). A highly significant increase in total, free and salivary cortisol was found within the first four hours after castration compared to the control group. The percentage increase one hour after castration above basal values was highest in free plasma cortisol (21.08 +/- 2.03 nmol/l vs. 61.26 +/- 4.16 nmol/l; 290.6%), and lowest in total plasma cortisol (177.33 +/- 9.69 nmol/l vs. 374.09 +/- 18.21 nmol/l; 211.0%), whereas salivary cortisol showed an 255.7% increase (10.46 +/- 1.03 nmol/l vs. 26.75 +/- 1.93 nmol/l). Total cortisol included 11.9-16.4% free cortisol. Salivary cortisol concentration was between 5.9% and 7.5% of the total plasma cortisol concentration. The highest correlation between total plasma cortisol and salivary cortisol occurred one hour after castration (r = 0.57; p < 0.01). The correlation between free and salivary cortisol was lowest for basal values (r = 0.27; p < 0.05), whereas correlations for the remaining time points were highly significant (0.41 < or = r < or = 0.61; p < 0.01). For the control group significant correlations were found between salivary and total plasma cortisol (0.58 < or = r < or = 0.89; p < 0.05) and between free and salivary cortisol (0.63 < or = r < or = 0.92; p < 0.05). The present work indicates that the measurement of salivary levels of cortisol reflects the concentration of this hormone in plasma samples of piglets.     

Restitution of blood volume after hemorrhage in dogs with adrenocortical suppression

Groups of splenectomized dogs were treated with weekly im doses of a potent glucocorticoid, methylprednisolone acetate (MPA; 2.5 mg/kg) or MPA-vehicle (controls) to determine if glucocorticoid-induced adrenocortical suppression would alter the restitution of blood volume in response to a 7.5 ml/kg hemorrhage. Five of the MPA-treated dogs were infused with cortisol (17 μg/min) for 2 hr beginning with the onset of hemorrhage. Blood volume restitution at 24 hr post-hemorrhage was reduced (P<0.05) in MPA-treated (46.5 ± 4.7%) or MPA-treated- cortisol infused (69.8 ± 9.7%) dogs as compared to controls (114 ± 11.8%). Hemorrhage was associated with a rapid increase in plasma immunoreactive (i) ACTH and cortisol concentrations in controls. In contrast, MPA treatment lowered baseline plasma iACTH and cortisol concentrations and prevented increases in either hormone following hemorrhage. Infusion of cortisol in one group of MPA-treated dogs gradually raised plasma cortisol concentrations but to lower (P<0.05) concentrations than measured in controls. Plasma aldosterone and glucose concentrations were not altered by MPA-treatment. Plasma osmolality increased to a greater (P<0.05) extent after hemorrhage in controls than in either group of MPA-treated dogs. It is concluded that glucocorticoid-induced adrenocortical suppression impairs the normal blood volume restitution process after moderate hemorrhage. The failure of cortisol infusion to fully restore restitution after MPA treatment may indicate that the pattern of the plasma cortisol response to hemorrhage is important in activating the restitution process or that MPA treatment diminishes non-cortisol dependent factors involved in restitution.     

24-Hour Profiles of Plasma Cortisol and Testosterone in the Male Dog: Absence of Circadian Rhythmicity, Seasonal Influence and Hormonal Interrelationships

Contents: Temporal changes of plasma cortisol and testosterone concentrations were measured in intact adult male beagle dogs during the spring and autumn with natural photoperiods of 16L:BD and 10L:14D, respectively. Each animal was fitted with an indwelling cephalic vein catheter and blood was withdrawn every 30 min for 24 h. Examination of the hormonal profiles revealed that both steroids are secreted episodically characterized by irregular short term fluctuations which were variable among different dogs. In several instances sustained elevations of cortisol and testosterone secretion occurred but were unrelated to photoperiod. Despite individual variability in the secretion patterns the daily means of each hormone were similar and not statistically different between spring and autumn .
When the 24 h were divided into three 8-h periods, namely 8.00–16.00 h (I), 16.00–24.00 h (II) and 24.00–8.00 h (III) overall and baseline mean cortisol and testosterone levels were not significantly different between the individual time periods. It appears that the dog differs from other species in that cortisol secretion was not related to the light-dark cycle. Concentrations of both hormones were not significantly correlated with each other throughout the sampling periods. Results from this study indicate that in intact male dogs cortisol and testosterone are secreted episodically without any evidence of circadian rhythmicity and seasonal variation and that an endocrine interrelationship between the adrenal cortex and the testis is not prominent under normal physiological conditions .     

Adrenal response to the low dose ACTH stimulation test and the cortisol-to-adrenocorticotrophic hormone ratio in canine babesiosis

This prospective, interventional, case-controlled study sought to determine the association between adrenocortical function and mortality in dogs with naturally occurring Babesia rossi babesiosis. Sixty-eight dogs with canine babesiosis were studied and fifteen normal dogs were used as controls. Blood samples were obtained from the jugular vein in each dog prior to treatment, at admission to hospital, for the measurement of basal plasma ACTH (adrenocorticotrophic hormone) and serum cortisol concentrations. Immediately thereafter, each dog was injected intravenously with 5 microg/kg of ACTH (tetracosactrin). A second blood sample was taken 1h later for serum ACTH-stimulated cortisol measurement and the resultant calculation of delta cortisol by subtracting basal from ACTH-stimulated cortisol. Diagnosis of babesiosis was confirmed by polymerase chain reaction (PCR) and reverse line blot (RLB). Three outcomes were defined: hospitalization with subsequent death (n=4); hospitalization followed by recovery (n=48); and treatment as an outpatient (n=16). Basal cortisol, but not ACTH-stimulated cortisol, was significantly higher in patients compared to control dogs. Basal- and ACTH-stimulated serum cortisol concentrations were significantly higher in the dogs that died, compared to hospitalized dogs that survived and compared to dogs treated as outpatients. There was no significant difference in delta cortisol concentrations or cortisol to ACTH ratios across outcome groups in dogs suffering from B. rossi babesiosis However, dogs with delta cortisol concentrations below 83 nmol/l had significantly higher cortisol to ACTH ratios compared to dogs with delta cortisol concentrations above 83 nmol/l. These findings of increased basal- and ACTH-stimulated cortisol and increased cortisol to ACTH ratios confirm the absence of adrenal insufficiency and concur with those in human malaria.     

Dynamik der LH- und Testosteron-Sekretion bei Beagle-Rüden verschiedener Altersgruppen*, **

Inhalt: Bei 1 7 klinisch geschlechtsgesunden Beagle-Rüden verschiedener Altersgruppen (1: 7 bis 8 Monate; II: 12 Monate; III: 23 Monate;IV: 3 bis 4 Jahre; V: 8 Jahre) wurden die Körper- und Hodenmaβe sowie die Sekretionsmuster von LH und Testosteron im peripheren Blutplasma bestimmt. Von jedem Ruden wurden im Abstand von 10 bis 14 Tagen zwei Blutprobenserien à 25 Einzelproben über einen Zeitraum von jeweils sechs Stunden unter Einhaltung 15 minütiger Intervalle gewonnen. Die Hodenlange war bei den 7 bis 8 Monate alten Tieren signifikant kleiner (p ≤ 0,01) als bei den älteren Rüden. Die 8 Jahre alten Hunde hatten die gröβten Gonaden. LH und Testosteron zeigten ein ausgeprägt pulsatiles Sekretionsmuster, wobei die LH-Werte zwischen 1,2 und 96 ng/ml und Testosteron zwischen 0,08 und 16 ng/ml varüerten. Die Pulsfrequenz unterschied sich nicht signifikant zwischen den Gruppen und lag im Mittel bei 4,5 Pulsen 16 Stunden. LH-Pulse wurden gewöhnlich von Testosteron-Pulsen gefolgt; der mittlere zeitliche Abstand zwischen beiden Ereignissen betrug 37 ± 15 Minuten. Die Plasmaproben der Gruppe I enthielten die höchsten LH- und die geringsten mittleren Testosteronkonzentrationen (15, 7 ± 13,6 ng/ml bzw. 2,0 ± 1,2 ng/ml). Das höchste durchschnittliche Testosteronniveau (3,6 ± 1,9 ng/ml) war in Gruppe III zu beobachten. Bei den 8 Jahre alten Hunden lag die mittlere LH-Konzentration signifikant unter derjenigen der 7 bis 8 und der 21 bis 23 Monate alten Tiere (p ± 0,01 bzw. p ± 0,05). Contents: Dynamics of LH and testosterone secretion in male beagles of different age In 17 clinically healthy male beagles of five age groups (I: 7 to 8 months, II: 12 months, III: 23 months, IV: 3 to 4 years, V: 8 years) the body size and the testicular dimensions were measured and the concentrations of LH and testosterone were determined in the peripheral blood. Two series of blood samples were collected from each dog with an interval of 10 to 14 days, each series consisting of 25 samples, taken every 15 minutes for 6 hours. The testicular length was significantly smaller (p ± 0.01) in the 7 to 8 months old dogs than in the older animals. The 8 year old dogs had the largest gonads. LH and testosterone secretion showed a marked pulsatility, with LH values ranging from 1.2 to 96 ng/ml and testosterone ranging from 0.08 to 16 ng/ml. Pulse frequency did not differ between groups and averaged 4,5 pulses/6 hours. LH pulses usually preceded testosterone pulses by an average of 37 ± 15 minutes. The samples of group I showed the highest mean LH concentration and the lowest mean testosterone value (15.7 ± 13.6 ng/ml and 2.0 ± 1.2 ng/ml resp.). The highest mean testosterone level (3.6 ± 1.9 ng/ml) was observed in group III. In the 8 year old dogs the mean LH-concentration was significantly lower than that of the animals aged 7 to 8 and 21 to 23 months (p ± 0.01 and p ± 0.05 resp.).     

Comparison between blood serum and salivary cortisol concentrations in horses using an adrenocorticotropic hormone challenge

Reasons for performing study: In horses, serum cortisol concentration is considered to provide an indirect measurement of stress. However, it includes both free and bound fractions. The sampling method is also invasive and often stressful. This is not the case for salivary cortisol, which is collected using a more welfare‐friendly method and represents a part of the free cortisol fraction, which is the biologically active form. Objectives: To compare salivary and serum cortisol assays in horses, in a wide range of concentrations, using an adrenocorticotropic hormone (ACTH) stimulation test, in order to validate salivary cortisol for stress assessment in horse. Methods: In 5 horses, blood samples were drawn using an i.v. catheter. Saliva samples were taken using swabs. Cortisol was assayed by radioimmunoassay. All data were treated with a regression method, which pools and analyses data from multiple subjects for linear analysis. Results: Mean ± s.d. cortisol concentrations measured at rest were 188.81 ± 51.46 nmol/l in serum and 1.19 ± 0.54 nmol/l in saliva. They started increasing immediately after ACTH injection and peaks were reached after 96 ± 16.7 min in serum (356.98 ± 55.29 nmol/l) and after 124 ± 8.9 min in saliva (21.79 ± 7.74 nmol/l, P<0.05). Discharge percentages were also different (225% in serum and 2150% in saliva, P<0.05). Correlation between serum and salivary cortisol concentrations showed an adjusted r²= 0.80 (P<0.001). The strong link between serum and salivary cortisol concentrations was also estimated by a regression analysis. Conclusions: The reliability of both RIAs and regression found between serum and salivary cortisol concentrations permits the validation of saliva‐sampling as a noninvasive technique for cortisol level assessment in horses.     

Effect of administration of adrenocorticotropic hormone on plasma concentrations of testosterone, luteinizing hormone, follicle stimulating hormone and cortisol in stallions

In boars and rabbits, administration of adrenocorticotropic hormone (ACTH) results in a testis-dependent, short-term increase in concentrations of testosterone in peripheral plasma. This experiment was designed to assess the short-term effects of a single ACTH injection on plasma concentrations of testosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH) and cortisol in stallions. Eight light horse and two pony stallions were paired by age and weight and then one of each pair was randomly assigned to the treatment (ACTH, .2 IU/kg of body weight) or control (vehicle) group. Injection of ACTH increased (P<.01) plasma concentrations of cortisol by approximately twofold in the first 60 minutes; control stallions showed no change (P>.10) in concentrations of cortisol during the blood sampling period. Control stallions exhibited a midday increase (P>.05) in concentrations of testosterone similar to that reported previously; ACTH treatment prevented or delayed this increase such that concentrations of testosterone in treated stallions were lower (P<.05) than in controls 4 to 5 hours after injection of ACTH. Treatment with ACTH had no effect (P<.10) on plasma concentrations of LH or FSH up to 12 hours after injection.     

Changes in the level of plasma cortisol, progesterone and total testosterone in developing hairless dogs.

Changes in the levels of plasma cortisol, progesterone and total testosterone were examined in developing hairless and haired dogs. Cortisol levels in the hairless dogs seemed to be higher than those in haired dogs within the age of 4-5 weeks. No apparent changes were seen in the level of plasma progesterone between the groups of hairless females and haired females. Total testosterone levels in hairless males showed to be significantly lower than those in haired males at the age of 13-21 weeks.     

Plasma free cortisol concentrations in dogs with hyperadrenocorticism.

Unbound or free cortisol constitutes a small fraction of total plasma cortisol, but is believed to represent the biologically active portion of this circulating glucocorticoid. We tested the hypothesis that the percentage free cortisol was altered in plasma from dogs with hyperadrenocorticism, which could account for a greater target tissue response to this circulating hormone. The percentage free cortisol in plasma samples from human beings, healthy dogs, and dogs with hyperadrenocorticism was estimated, using centrifugal ultrafiltration-dialysis. Total cortisol concentrations were determined by use of radioimmunoassay. Total cortisol concentrations appeared greater in plasma from human beings than in plasma from either group of dogs. However, the percentage free cortisol was lower in plasma from human beings, resulting in a calculated concentration of free cortisol that was quite similar between plasma from human beings and healthy dogs. Total plasma cortisol concentrations were greater (P less than 0.01) in samples from dogs with hyperadrenocorticism (190 +/- 113 nmol/L; mean +/- SD) than in healthy dogs (102 +/- 85 nmol/L), but the percentage free cortisol was not different between these 2 groups (dogs with hyperadrenocorticism, 16 +/- 9%; healthy dogs, 13 +/- 6%). However, plasma free cortisol concentrations (product of total and the percentage of free cortisol) were greater (P less than 0.01) in samples from dogs with hyperadrenocorticism (36 +/- 41 nmol/L) than in those from healthy dogs (16 +/- 9 nmol/L). Significant (P less than 0.001) positive linear relationships were found between total cortisol concentrations and percentage free cortisol in plasma samples from healthy dogs and dogs with hyperadrenocorticism.(ABSTRACT TRUNCATED AT 250 WORDS)     

Communications: Validation of a Solid-Phase Enzyme Immunoassay Technique for the Measure of Plasma Cortisol in Rainbow Trout

Abstract

A kit for a solid-phase enzyme immunoassay (SOPHEIA®) of cortisol in human sera was evaluated and validated for measuring cortisol in plasma of rainbow trout Oncorhynchus mykiss. The accuracy of the SOPHEIA was demonstrated by the recovery of exogenous cortisol concentrations of 25, 50, 100, and 250 ng/mL in charcoal-stripped fish plasma. The amounts (mean ± SE) recovered from triplicate samples were 29.9 ± 2.75, 47.5 ± 3.41, 101.7 ± 12.08, and 232.0 ± 11.06 ng/mL, respectively. The intra- and interassay coefficient of variation (CV = 100 × SD/mean) for cortisol levels in undisturbed fish (26.6 ± 1.18 ng/mL) were 14 and 10%, respectively. The intra- and interassay CV for elevated cortisol levels in stressed fish (330.8 ± 19.90 ng/mL) were 8 and 13%, respectively. Cross-reactivity determined for nine steroids in teleostean fish was negligible. Cortisol concentrations in serial dilutions of pooled fish plasma were parallel to the standard curve. Sensitivity (minimum detection limit) was 3.04 ng/mL. The SOPHEIA compared favorably to radioimmunoassay measurements of cortisol (r = 0.98; P < 0.001).     

Validation of a commercially available enzyme-linked immunosorbent assay (ELISA) for the determination of cortisol in canine plasma samples

Samples were obtained from clinically normal dogs before and after ACTH stimulation and dexamethasone suppression tests. The test kit Enzymun-Test (Boehringer Mannheim) for determining cortisol concentrations in human plasma was used in connection with the analyser system Enzymun-Test (Boehringer Mannheim) System ES300 following the manufacturer's instructions. The intra-assay and inter-assay coefficients of variation were 1.28% and 5.64%, respectively. The mean recovery when assaying samples with a cortisol content of more than 100 nmol/L was 95.41%, but this percentage decreased in samples with lower cortisol levels. The sensitivity of the assay was 2.76 nmol/L. The results of the ACTH stimulation and dexamethasone suppression tests were similar to those published previously. The ELISA method evaluated allows a precise and sensitive determination of cortisol concentrations in canine plasma samples. The major drawback observed was the loss of accuracy at low cortisol concentrations. Since the assay tends then to report lower cortisol concentrations, the generally accepted concentration of 40 nmol/L may not be suitable as the cutoff value in dexamethasone suppression tests.     

Comparison of postoperative effects between lidocaine infusion,meloxicam, and their combination in dogs undergoing ovariohysterectomy

ObjectiveTo compare the postoperative analgesic effects of intravenous (IV) lidocaine, meloxicam, and their combination in dogs undergoing ovariohysterectomy.Study designProspective, randomized, double‐blind, controlled clinical trial.AnimalsTwenty‐seven dogs aged (mean ± SD) 16.1 ± 7.5 months and weighing 22.4 ± 17.9 kg scheduled for ovariohysterectomy.MethodsAnaesthesia was induced with propofol and maintained with isoflurane. Dogs (n = 9 in each group) were allocated to receive just prior to and during surgery one of the following regimens: M group, 0.2 mg kg^?1 IV meloxicam then a continuous rate infusion (CRI) of lactated Ringer's at 10 mL kg^?1 hour^?1; L group, a bolus of lidocaine (1 mg kg^?1 IV) then a CRI of lidocaine at 0.025 mg kg^?1 minute^?1; and M + L group, both the above meloxicam and lidocaine treatments. Pain and sedation were scored, and venous samples taken for serum cortisol and glucose measurement before and at intervals for 12 hours after anaesthesia. Pain scores were assessed using a multi‐parameter subjective scoring scale (cumulative scale 0–21) by three observers. The protocol stated that dogs with a total score exceeding 9 or a sub‐score above 3 in any one category would receive rescue analgesia. Sedation was scored on a scale of 0–4.ResultsThere were no significant differences in subjective pain scores, serum cortisol, and glucose concentrations between the three groups. The highest pain score at any time was 5, and no dog required rescue analgesia. None of the three regimens caused any observable side effects during or after anaesthesia. At 1 and 2 hours after extubation dogs in group L were significantly more sedated than in the other two groups.Conclusions and Clinical relevanceThis study suggests that, with the scoring system used, IV lidocaine and meloxicam provide similar and adequate post‐operative analgesia in healthy dogs undergoing ovariohysterectomy.     

Induced gonadotropin release in adrenocorticotropin-treated bulls and steers

The effect of adrenocorticotropin hormone (ACTH) on plasma cortisol and on gonadotropin releasing hormone (GnRH)-induced release of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone was determined in nine Holstein bulls and 12 Holstein steers. Treatments consisted of animals receiving either GnRH (200 micrograms, Group G), ACTH (.45 IU/kg BW, Group A) or a combination of ACTH followed 2 h later by GnRH (Group AG). Group G steers and bulls had elevated plasma LH and FSH within .5 h after GnRH injection and plasma testosterone was increased by 1 h after GnRH injection in bulls. In Group A, plasma cortisol was elevated by .5 h after ACTH injection in both steers and bulls, but plasma LH and FSH were unaffected. In Group A bulls, testosterone was reduced after ACTH injection. In Group AG, ACTH caused an immediate increase in plasma cortisol in both steers and bulls, but did not affect the increase in either plasma LH or FSH in response to GnRH in steers. In Group AG bulls, ACTH did not prevent an increase in either plasma LH, FSH or testosterone in response to GnRH compared with basal concentrations. However, magnitude of systemic FSH response was reduced compared with response in Group G bulls, but plasma LH and testosterone were not reduced. The results indicate that ACTH caused an increase in plasma cortisol, but did not adversely affect LH or FSH response to GnRH in steers and bulls. Further, while testosterone was decreased after ACTH alone, neither ACTH nor resulting increased plasma cortisol resulted in decreased testosterone production in the bull after GnRH stimulation.     

Effects of hemolysis and storage on quantification of hormones in blood samples from dogs, cattle, and horses

Veterinary diagnostic endocrinology laboratories frequently receive hemolyzed plasma, serum, or blood samples for hormone analyses. However, except for the previously reported harm done by hemolysis to canine insulin, effects of hemolysis on quantification of other clinically important hormones are unknown. Therefore, these studies were designed to evaluate effects of hemolysis on radioimmunoassay of thyroxine, 3,5,3'-triiodothyronine, progesterone, testosterone, estradiol, cortisol, and insulin in equine, bovine, and canine plasma. In the first experiment, hormones were measured in plasma obtained from hemolyzed blood that had been stored for 18 hours. Blood samples were drawn from pregnant cows, male and diestrous female dogs, and male and pregnant female horses. Each sample was divided into 2 equal portions. One portion was ejected 4 times with a syringe through a 20-gauge (dogs, horses) or 22-gauge (cows) hypodermic needle to induce variable degrees of hemolysis. Two subsamples of the blood were taken before the first and after the first, second, and fourth ejections. One subsample of each pair was stored at 2 to 4 C and the other was stored at 20 to 22 C for 18 to 22 hours before plasma was recovered and stored at -20 C. The second portion of blood from each animal was centrifuged after collection; plasma was recovered and treated similarly as was blood. Concentrations of thyroxine in equine plasma, of 3,5,3'-triiodothyronine, estradiol, and testosterone in equine and canine plasma, and of cortisol in equine plasma were not affected by hemolysis.(ABSTRACT TRUNCATED AT 250 WORDS)