Leptin stimulates hepatic activation of thyroid hormones and promotes early posthatch growth in the chicken

Hepatic iodothyronine deiodinases (Ds) are involved in the conversion of thyroid hormones (THs) which interacts with growth hormone (GH) to regulate posthatch growth in the chicken. Previous studies suggest that leptin-like immunoreactive substance deposited in the egg may serve as a maternal signal to program posthatch growth. To test the hypothesis that maternal leptin may affect early posthatch growth through modifying hepatic activation of THs, we injected 5.0μg of recombinant murine leptin into the albumen of breeder eggs before incubation. Furthermore, chicken embryo hepatocytes (CEHs) were treated with leptin in vitro to reveal the direct effect of leptin on expression and activity of Ds. In ovo leptin administration markedly accelerated early posthatch growth, elevated serum levels of total and free triiodothyronine (tT3 and fT3), while that of total thyroxin (tT4) remained unchanged. Hepatic mRNA expression and activity of D1 which converts T4 to T3 or rT3 to T2, were significantly increased in leptin-treated chickens, while those of D3 which converts T3 to T2 or T4 to rT3, were significantly decreased. Moreover, hepatic expression of GHR and IGF-I mRNA was all up-regulated in leptin-treated chickens. Males demonstrated more pronounced responses. A direct effect of leptin on Ds was shown in CEHs cultured in vitro. Expression and activity of D1 were increased, whereas those of D3 were decreased, in leptin-treated cells. These data suggest that in ovo leptin administration improves early posthatch growth, in a gender-specific fashion, probably through improving hepatic activation of THs and up-regulating hepatic expression of GHR and IGF-I.     

Thyroid hormones in grey seal pups (Halichoerus grypus).

The aim of the present study was to describe the changes in thyroid hormone status in grey seal (Halichoerus grypus) pups from birth to weaning and moulting. Plasma concentrations of total thyroxine (tT4) were highest the first two days after birth, thereafter dropping to a lower, but stable level. This pattern may reflect a high transfer rate of maternal thyroxine prepartum, prior to parturition, or postpartum via colostrum, or it may be caused by active secretory thyrocytes in late foetal stage. Total triiodothyronine (tT3) concentrations were lowest in neonatal pups, and increased as a function of age, indicating that deiodination of T4 to T3 increases as a function of age. Plasma concentrations of free thyroxine (fT4) did not vary as a function of age. All hormone concentrations were higher than previously reported in adults, probably reflecting the important role of these hormones in regulating their high rates of metabolism and tissue synthesis and the growth of their juvenile pelage. Since polychlorinated biphenyls (PCBs) have been reported to affect plasma concentrations of thyroid hormones in seals, the information on thyroid hormone concentrations and dynamics reported in grey seal pups from a pristine Norwegian coastal environment provide valuable reference material for future studies on pups from more polluted areas.     

Low-T3 syndrome and signal-averaged ECG in haemodialysed patients

The study was designed to evaluate the potential link between low-T3 syndrome and signal-averaged ECG parameters (SAECG) in a group of hemodialyzed patients (HD-pts). 52 selected HD-pts (without relevant thyroid and cardiac diseases) were included. SAECGs were performed postdialysis together with evaluating free triiodothyronine (fT3), free thyroxine (fT4), reverse triiodothyronine (rT3), thyroid stimulating hormone levels and echocardiography. For each SAECG, QRS duration (QRSd), root-mean-square voltage of the terminal 40 ms of the QRS (RMS40), and low-amplitude signal duration (LAS40) were measured. Abnormal SAECGs were found in 30.8 % of HD-pt. HD-pts with decreased fT3 and increased rT3 values (low-T3 positive) revealed higher QRSd and LAS40 values in comparison with low-T3 negative HD-pts (p = 0.019, p < 0.001 respectively). Low-T3 positive HD-pts had lower RMS40 values than low-T3 negative patients (p < 0.001). The Pearson test showed significant correlations between QRSd and fT3 (r = -0.592, p < 0.001); QRSd and rT3 (r = 0.562, p < 0.001); RMS40 and fT3 (r = 0.432, p = 0.009); RMS40 and rT3 (r = -0.325, p = 0.025). On multivariate analysis, both fT3 and rT3 levels were found to be independent predictors of QRSd and RMS40 values. Our study showed that decreased fT3 and increased rT3 concentrations due to low-T3 syndrome influence SAECG parameters in HD-pt.     

Hormones and metabolites of arctic foxes (Alopex lagopus) in response to season, starvation and re-feeding

Svalbard's arctic foxes experience large seasonal variations in light, temperature and food supply throughout the year, which may result in periods of starvation. The aim of this work is to investigate if there are seasonal variations in post-absorptive plasma thyroid hormones (free thyroxin (fT(4)), free triiodothyronine (fT(3)) and reverse triiodothyronine (rT(3))) and metabolites (free fatty-acids (FFA) and beta-hydroxybutyrate (beta-OHB)) with season and their response to starvation and re-feeding. The concentrations of post-absorptive free triiodothyronine were significantly higher in November than May, while those of thyroxin, reverse triiodothyronine, free fatty-acids and beta-hydroxybutyrate remained unchanged. Possible explanations for the seasonal variations in free triiodothyronine are discussed. There were no significant changes from post-absorptive concentrations of thyroxin and reverse triiodothyronine in starved and re-fed foxes. However, free triiodothyronine concentrations decreased during starvation and increased again with re-feeding both in May and November. Starvation induced high levels of free fatty acids in both May and November, indicating increased lipolysis. There was a significant increase in beta-hydroxybutyrate in November only, indicating that arctic foxes are capable of protein conservation during starvation.     

TRH test in patients with diabetes mellitus type 1 and/or autoimmune thyroiditis. Changes in the pituitary-thyroid axis, reverse T3, prolactin and growth hormone levels

The response of the pituitary- thyroid axis, reverse triiodothyronine (rT3), prolactin, and growth hormone (GH) levels following TRH stimulus (Relefact TRH 200 microg 2 amp. i.v.) was examined in patients with autoimmune diabetes type 1 (DM1, n=30), with autoimmune thyroiditis (AT, n=25), and with concurrent DM1 and AT (n=22) to evaluate the influence of DM1 and AT of autoimmune pathogenesis on the above-mentioned hormonal parameters. Statistical analysis (ANOVA) showed that: a) the response of TSH did not differ from control groups (C); b) free triiodothyronine (fT3), free thyroxine (fT4) and their ratio in DM1, DM1+AT and C rose in 120 and 180 min, while a similar increase was not seen in AT (p<0.000001); c) rT3 was not present in any group, with rT3 levels higher in AT (p<0.00002) and lower in DM1 (p<0.02); d) the response of GH had a paradoxical character in some patients in all groups, most often in DM1 (52 %, DM1 vs C, p <0.01). The characteristic response difference was not in the peak GH level, but the delayed return to basal levels in DM1 (p<0.0001) and an abrupt one in AT (p<0.0001). The major findings in DM1 were the differences in GH response, while significant impairment of pituitary-thyroid axis and PRL response to TRH was absent. AT was associated with impairment of TRH stimulated fT3, fT4, fT3/fT4 response and changes in rT3 levels, in spite of preserved TRH-stimulated TSH secretion. GH response in AT patients was also altered.     

Adrenal Hormones in Common Bottlenose Dolphins (Tursiops truncatus): Influential Factors and Reference Intervals

Inshore common bottlenose dolphins (Tursiops truncatus) are exposed to a broad spectrum of natural and anthropogenic stressors. In response to these stressors, the mammalian adrenal gland releases hormones such as cortisol and aldosterone to maintain physiological and biochemical homeostasis. Consequently, adrenal gland dysfunction results in disruption of hormone secretion and an inappropriate stress response. Our objective herein was to develop diagnostic reference intervals (RIs) for adrenal hormones commonly associated with the stress response (i.e., cortisol, aldosterone) that account for the influence of intrinsic (e.g., age, sex) and extrinsic (e.g., time) factors. Ultimately, these reference intervals will be used to gauge an individual’s response to chase-capture stress and could indicate adrenal abnormalities. Linear mixed models (LMMs) were used to evaluate demographic and sampling factors contributing to differences in serum cortisol and aldosterone concentrations among bottlenose dolphins sampled in Sarasota Bay, Florida, USA (2000–2012). Serum cortisol concentrations were significantly associated with elapsed time from initial stimulation to sample collection (p<0.05), and RIs were constructed using nonparametric methods based on elapsed sampling time for dolphins sampled in less than 30 minutes following net deployment (95% RI: 0.91–4.21 µg/dL) and following biological sampling aboard a research vessel (95% RI: 2.32–6.68 µg/dL). To examine the applicability of the pre-sampling cortisol RI across multiple estuarine stocks, data from three additional southeast U.S. sites were compared, revealing that all of the dolphins sampled from the other sites (N = 34) had cortisol concentrations within the 95th percentile RI. Significant associations between serum concentrations of aldosterone and variables reported in previous studies (i.e., age, elapsed sampling time) were not observed in the current project (p<0.05). Also, approximately 16% of Sarasota Bay bottlenose dolphin aldosterone concentrations were below the assay’s detection limit (11 pg/mL), thus hindering the ability to derive 95th percentile RIs. Serum aldosterone concentrations from animals sampled at the three additional sites were compared to the detection limit, and the proportion of animals with low aldosterone concentrations was not significantly different than an expected prevalence of 16%. Although this study relied upon long-term, free-ranging bottlenose dolphin health data from a single site, the objective RIs can be used for future evaluation of adrenal function among individuals sampled during capture-release health assessments.     

Evaluation of endothelial dysfunction, lipid metabolism in women with polycystic ovary syndrome: relationship of paraoxonase 1 activity, malondialdehyde levels, low-density lipoprotein subfractions, and endothelial dysfunction

The aim of this study was to assess relationship of insulin resistance, oxidant-antioxidant status, endothelial dysfunction, lipid metabolism, and their contribution to the risks of cardiovascular disease in women with polycystic ovary syndrome (PCOS). Forty-five women with PCOS and 17 healthy women were included in this study. Nitric oxide (NO), endothelin-1 (ET-1), malondialdehyde (MDA), Apo A1, Apo B, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglyceride, small, dense LDL cholesterol (sdLDL-C), large buoyant LDL cholesterol (LbLDL-C) levels, and paraoxonase 1 (PON1) activity were measured in serum/plasma obtained from study groups. Insulin resistance [homeostasis model assessment (HOMA) index] and serum sex hormone binding globulin (SHBG), total testosterone (tT), free testosterone (fT), androstenedione, and dehydroepiandrosteronsulfate (DHEAS) levels were also evaluated. Significantly decreased SHBG, NO, HDL-C levels, and PON1 activities, but increased tT, fT, androstenedione, DHEAS, HOMA index, MDA, ET-1, LDL-C, sdLDL-C, and LbLDL-C values were found in PCOS patients compared with those of controls. There was a positive correlation between MDA and fT levels; and a negative correlation between PON1 activity and fT. Our data show that insulin resistance, dyslipidemia, endothelial dysfunction, and oxidative stress might contribute to the excess risk of cardiovascular disease reported in PCOS patients.     

Unusual features of neonatal thyroid function in small-for-gestational-age lambs. Origin of plasma T4 and T3 deficiencies

Thyroid function was studied in small for gestational age (SGA) or control newborn lambs. Neonatal changes in plasma concentrations of TSH, T3, rT3, total and free T4 were monitored, and thyroid scintigraphs were performed. Responsiveness of the hypothalamic-pituitary-thyroid axis to cold exposure and TRH or TSH administration was assessed. In addition, T4 and T3 kinetic studies were performed. In agreement with results obtained in babies, plasma T3, total T4 and free T4 concentrations were depressed in low birth weight animals, whereas TSH and rT3 levels were not affected. Thyroid size expressed relatively to the body weight was higher in SGA animals, thus suggesting that a partial compensation for low thyroid hormone levels had occurred during the fetal life. Plasma TSH and T4 concentrations increased by a same extent after exposure to cold and TRH or TSH administration in SGA and control lambs; however, the rise in T3 levels was depressed in the former in all stimulation tests. T3 and T4 production rates were similar in the two experimental groups. In SGA lambs, the metabolic clearance rate and the total distribution space of these two hormones were significantly increased; the fast T3 pool was higher, and the slow T3 pool lower than in control animals. All these results demonstrate that, despite low circulating thyroid hormone concentrations, SGA lambs are not hypothyroid. An increased T4 and T3 storage in the extravascular compartment is probably the major factor involved in the occurrence of this plasma deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of prolonged fasting on plasma cortisol and TH in postweaned northern elephant seal pups

Northern elephant seal (Mirounga angustirostris) pups rely on the oxidation of fat stores as their primary source of energy during their 8- to 12-wk postweaning fast; however, potential endocrine mechanisms involved with this increased fat metabolism have yet to be examined. Therefore, 15 pups were serially blood sampled in the field during the first 7 wk of their postweaning fast to examine the changes in plasma concentrations of cortisol and thyroid hormones (TH), which are involved in fat metabolism in other mammals. Cortisol increased, indicating that it contributed to an increase in lipolysis. Increased total triiodothyronine (tT(3)) and thyroxine (tT(4)) may not reflect increased thyroid gland activity, but rather alterations in hormone metabolism. tT(3)-to-tT(4) ratio decreased, suggesting a decrease in thyroxine (T(4)) deiodination, whereas the negative correlation between total proteins and free T(4) suggests that the increase in free hormone is attributed to a decrease in binding globulins. Changes in TH are most similar to those observed during hibernation than starvation in mammals, suggesting that the metabolic adaptations to natural fasting are more similar to hibernation despite the fact these animals remain active throughout the fasting period.     

Response to capture stress involves multiple corticosteroids and is associated with serum thyroid hormone concentrations in Guadalupe fur seals (Arctocephalus philippii townsendi)

Guadalupe fur seals are a threatened species with few breeding locations, which potentially makes them sensitive to environmental or anthropogenic stressors. We present the first study to quantify adrenal and thyroid function in this species in an effort to measure their stress response to capture. We analyzed a suite of corticosteroid hormones released over time during capture in both adult females (n = 10) and weanling pups (n = 26) during March 2016. Multiple corticosteroids were released during capture, and aldosterone was associated with the response to stress in adults only. These results suggest the regulation of aldosterone secretion in association with the HPA axis in otariids as reported in other marine mammals. Individuals varied markedly in the magnitude of their endocrine response to capture. A lower total integrated stress response to capture for both cortisol and corticosterone was associated with decreased concentrations of thyroid hormone T3 and elevated concentrations of reverse T3 (rT3), suggesting parallel downregulation of adrenal and thyroid endocrine axes in some individuals. A scaled body condition index was negatively associated with T3 and positively associated with rT3 in adults. Together these findings suggest utility in using endocrine responses to capture stress to evaluate individual and population health.     

Free Thyroxine During Early Pregnancy and Risk for Gestational Diabetes

Several studies have now reported associations between gestational diabetes mellitus (GDM) and low free thyroxine (fT4) during the second and third trimesters, but not in the first trimester. The present study further examines relationships between low fT4, maternal weight, and GDM among women in the FaSTER (First and Second Trimester Evaluation of Risk) trial, in an effort to determine the extent to which thyroid hormones might contribute to causality. The FaSTER cohort includes 9351 singleton, euthyroid women; 272 of these women were subsequently classified as having GDM. Thyrotropin (TSH), fT4, and thyroid antibodies were measured at 11–14 weeks’ gestation (first trimester) and 15–18.9 weeks’ gestation (second trimester). An earlier report of this cohort documented an inverse relationship between fT4 in the second trimester and maternal weight. In the current analysis, women with GDM were significantly older (32 vs. 28 years) and weighed more (75 vs. 64.5 kg). Maternal weight and age (but not TSH) were significantly associated univariately with fT4 (dependent variable), in the order listed. Second trimester fT4 odds ratios (OR) for GDM were 2.06 [95% CI 1.37–3.09] (unadjusted); and 1.89 [95% CI 1.26–2.84] (adjusted). First trimester odds ratios were not significant: OR 1.45 [95%CI 0.97–2.16] (unadjusted) and 1.11 [95% CI 0.74–1.62] (adjusted). The second trimester fT4/GDM relationship thus appeared to strengthen as gestation progressed. In FaSTER, high maternal weight was associated with both low fT4 and a higher GDM rate in the second trimester. Peripheral deiodinase activity is known to increase with high caloric intake (represented by high weight). We speculate that weight-related low fT4 (the metabolically inactive prohormone) is a marker for deiodinase activity, serving as a substrate for conversion of fT4 to free triiodothyronine (fT3), the active hormone responsible for glucose-related metabolic activity.     

Relationship between pituitary-thyroid axis hormones and anthropometric parameters in Czech adult population

Although the relationships between thyroid function and anthropometric parameters were studied in patients with thyroid disorders and in morbidly obese subjects, such data in normal healthy population are scarce. In our study, relationships between factors of body composition, fat distribution and age with hormones of the pituitary-thyroid axis were evaluated in a large, randomly selected sample of normal adult Czech population comprising of 1012 men and 1625 women. Our results exhibited weak, but significant relationships between body composition, body fat distribution and the parameters of pituitary-thyroid axis. Some of these associations were gender-specific. As shown by backward stepwise regression model, body fat distribution evaluated by centrality index (subscapular/triceps skinfold ratio) was negatively associated with free triiodothyronine (fT3) serum levels only in women, while a positive correlation of fT3 with BMI was specific for men. BMI was inversely related to free thyroxine (fT4) concentrations in women but not in men. The centrality index (CI) was positively related to TSH levels in both genders. The fT3/fT4 ratio, reflecting deiodinase activity, was inversely related to age and positively related to BMI in both genders, while the highly significant negative correlation between CI and fT3/fT4 ratio was specific for women.     

Weight Loss Through Gastric Banding: Effects on TSH and Thyroid Hormones in Obese Subjects With Normal Thyroid Function

Studies on thyroid function in obesity yielded inconsistent results; high thyroid‐stimulating hormone (TSH) levels were generally shown; high free triiodothyronine (fT)‐3 or fT4 levels were described in some, but not in other studies. After weight loss, TSH and thyroid hormones have been described to either increase or decrease. Our aim was to describe TSH, fT3, and fT4 in obese subjects with normal thyroid function before and after durable and significant weight loss, obtained through laparoscopic gastric banding (LAGB), in comparison with nonobese subjects. TSH, fT3, fT4, and fT3/fT4 ratio (an index of D1 and D2 deiodinase activity), were evaluated in 99 healthy controls and in 258 obese subjects, at baseline and 6 months, 1 year, and 2 years after LAGB, together with indexes of glucose (glucose, insulin, homeostasis model assessment of insulin resistance index) and lipid (triglycerides, total and high‐density lipoprotein–cholesterol) metabolism, and anthropometric measures (BMI and waist circumference). Under basal conditions, TSH, fT3, and fT4 were all in the normal range, but higher in obese than in nonobese subjects, and fT3/fT4 ratio was normal; with weight loss, fT3 and fT3/fT4 ratio decreased in obese subjects, while fT4 increased and TSH remained steady; all values were again within the normal range. Albumin and cholesterol levels remained steady, while triglycerides, insulin, and homeostasis model assessment of insulin resistance decreased, and high‐density lipoprotein–cholesterol increased. These changes, however, do not modify TSH, letting us to hypothesize that the changes are due to a decrease of D1 and D2 deiodinase activities.     

Anticonvulsants and thyroid function.

Serum total and free thyroid hormone concentrations were estimated in 42 patients with epilepsy taking anticonvulsants (phenytoin, phenobarbitone, and carbamazepine either singly or in combination). There was a significant reduction in total thyroxine (TT4), free thyroxine (FT4), and free triiodothyronine (FT3) in the treated group compared with controls. Free hormone concentrations were lower than total hormone concentrations, suggesting that increased clearance of thyroid hormones occurs in patients receiving anticonvulsants. Detailed analysis indicated that phenytoin had a significant depressant effect on TT4, FT4, FT3, and reverse T3 (rT3). Phenobarbitone and carbamazepine had no significant main effects, but there were significant interactions between phenytoin and carbamazepine for TT4 and FT4. phenobarbitone and carbamazepine for FT3, and phenytoin and phenobarbitone for rT3.     

The Interaction Between Selenium Status, Sex Hormones, and Thyroid Metabolism in Adolescent Girls in the Luteal Phase of their Menstrual Cycle

The objective of the present work was to study all physiological relationships among selenium status (SeS), sex hormones secretion (SH), and thyroid metabolism (ThM) in healthy adolescent girls, at one time. Forty-four girls aged 13.4–16.6 years (mean age, 14.5 ± 0.5 years) entered the statistical model. Parameters reflecting SeS: plasma selenium concentration (Se) and plasma glutathione peroxidase activity (GPX3); SH: serum estradiol (E₂) and progesterone (P₄); age of menarche (AoM); and ThM: thyroid stimulating hormone (TSH), free thyroxine (fT4), free triiodothyronine (fT3), antithyroid peroxidase antibodies (anti-TPO) in serum, and thyroid volume (ThV), were determined, and the interactions between them were evaluated by means of the partial least squares method (PLS). PLS method was, for the first time, successfully applied to the problem of selenium and hormone interactions and revealed that selenium status and female reproductive system are interrelated and affect thyroid physiology in adolescent girls in the luteal phase. The strongest associations were revealed for the pairs of parameters, Se and fT4/fT3, Se and P₄, the modest ones for the pairs, Se and ThV, P₄ and fT4/fT3, Se and AoM, and P₄ and AoM. There was no correlation between E₂, GPX3, and TSH, and any other considered parameter. Se and P₄ had the greatest influence on ThM parameters.     

Maternal thyroid hormone trajectories during pregnancy and child behavioral problems

There is ample evidence demonstrating the importance of maternal thyroid hormones, assessed at single trimesters in pregnancy, for child cognition. Less is known, however, about the course of maternal thyroid hormone concentrations during pregnancy in relation to child behavioral development. Child sex might be an important moderator, because there are sex differences in externalizing and internalizing behavioral problems. The current study examined the associations between maternal thyroid hormone trajectories versus thyroid assessments at separate trimesters of pregnancy and child behavioral problems, as well as sex differences in these associations. In 442 pregnant mothers, serum levels of TSH and free T4 (fT4) were measured at 12, 24, and 36 weeks gestation. Both mothers and fathers reported on their children's behavioral problems, between 23 and 60 months of age. Latent growth mixture modeling was used to determine the number of different thyroid hormone trajectories. Three trajectory groups were discerned: 1) highest and non-increasing TSH with lowest fT4 that decreased least of the three trajectories; 2) increasing TSH and decreasing fT4 at intermediate levels; 3) lowest and increasing TSH with highest and decreasing fT4. Children of mothers with the most flattened thyroid hormone trajectories (trajectory 1) showed the most anxiety/depression symptoms. The following trimester-specific associations were found: 1) lower first-trimester fT4 was associated with more child anxiety/depression, 2) higher first-trimester TSH levels were related to more attention problems in boys only. A flattened course of maternal thyroid hormone concentrations during pregnancy was a better predictor of child anxiety/depression than first-trimester fT4 levels.     

Effects of capture on adrenal steroid and vasopressin concentrations in free-ranging bottlenose dolphins (Tursiops truncatus)

Marine mammals are routinely caught in the wild in an effort to monitor their health. However, capture-associated stress could potentially bias various biochemical parameters used to monitor the health of these wild caught animals. Therefore, the effects of capture were quantified by measuring plasma adrenal steroids and arginine vasopressin (AVP) in free-ranging bottlenose dolphins (Tursiops truncatus) (n=31). Total capture and restraint times were also correlated to hormone concentrations to quantify the effects of capture. Significant, positive correlations between corticosterone and cortisol (R=0.752; P<0.0001), and between corticosterone and aldosterone (R=0.441; P=0.045) were demonstrated. Significant correlations between capture and restraint time and hormone levels were not observed. Animals restrained for less than 20 min exhibited hormone levels similar to those for animals restrained for more than 20 min. The positive correlations among the adrenal steroids suggest that release of these steroids was stimulated by adrenocorticotropin (ACTH). The lack of a correlation between cortisol and AVP indicates that AVP did not influence ACTH-induced cortisol release in this situation. The study suggests that (1) a typical hypothalamic-pituitary-adrenal axis is present in these animals, and (2) the relatively short capture and restraint times did not induce a significant neuroendocrine stress response.     

Evaluation of adrenal function in rats by the measurement of urinary free corticosterone, free aldosterone and free 11-deoxycorticosterone.

Methods für the determination of urinary free corticosterone, free aldosterone and free 11-deoxycorticosterone (DOC) in rats are described. The free corticosteroids were measured in urine samples of 0.1–0.5 (2.0) ml by radioimmunoassay after purification by column chromatography. The validity of the methods is demonstrated by the data of the free urinary corticoids under basal conditions and after adrenal suppression and various forms of adrenal stimulation. The basal excretion of free corticosterone, free aldosterone and free DOC was 123.71 ± 15.31 (x? ± SD), 3.87 ± 1.29 and 10.61 ± 2.24 ng/day, respectively, exhibiting a decrease to 26.20 ± 5.21, 1.05 ± 0.47 and 1.35 ± 1.20 ng/day after adrenal suppression by dexamethasone. Irrespective of the mode of adrenal stimulation i.e., synthetic ACTH and systemic (cold, hunger) or neurotrophic (ether, reserpine) stress stimuli free corticosterone increased to about 450 ng/day, while free aldosterone excretion decreased during hunger and cold and was strongly enhanced after the application of reserpine. Furthermore, determination of urinary free DOC, which increased by a factor of 4, may be applied in the metyrapone test. There was a good correlation between the excretion of free corticosterone and that of free aldosterone and free DOC under basal conditions and after ACTH application, demonstrating that ACTH is responsible for the secretion of all the 3 corticoids measured. It is concluded, that the measurement of the urinary excretion of corticosterone, aldosterone and DOC is a valuable parameter of adrenal function in rats. Furthermore, in small laboratory animals like rats steroid measurements in urine are often more advantageous than Measurements in plasma.     

Radioimmunoassay of serum follicle-stimulating hormone and luteinizing hormone in the bottlenosed dolphin

Commercially available radioimmunoassay (RIA) kits for human follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were adapted for quantitation of these hormones in serum from bottlenosed dolphins (Tursiops truncatus). Serum samples from over 160 wild and 70 captive animals were assayed in order to determine basal concentrations of FSH and LH in these animals, as well as to detect possible differences between various groups. Mean FSH and LH levels for all animals were 0.22 +/- 0.08 and 0.37 +/- 0.18 ng/ml, respectively. Although wild animals had higher FSH and LH levels than captive ones, the differences were not statistically significant (P less than 0.07). However, both FSH and LH were significantly (P less than 0.01 and P less than 0.05, respectively) elevated in females when compared to males. Adults and peripubescent animals had significantly (P less than 0.01) higher LH levels than did juveniles. Among wild animals, serum concentrations of FSH and LH reflected seasonal differences. Samples obtained in early summer (Gulf of Mexico population) contained significantly (P less than 0.01) higher concentrations of FSH and LH than samples obtained in the fall (Indian River, Florida population). Both FSH and LH were significantly elevated in samples from confirmed pregnant animals as compared to the overall mean and to a sample from a confirmed nonpregnant female. Our observations indicate that these RIAs can reliably detect serum FSH and LH from bottlenosed dolphins and represent the first quantitation of these hormones in cetaceans.     

Physiological variables of horses after road transport

In order to investigate the effects of short road transport stress on total and free iodothyronines, body weight (BW), rectal temperature and heart rate (HR) changes, 126 healthy stallions were studied in basal conditions, before and after transport. A total of 60 Thoroughbred and 66 crossbred stallions aged 4 to 15 years with previous travelling experience were transported by road in a commercial trailer for a period of about 3 to 4 h (distance under 300 km). Blood samples and functional variables were collected in each horse box, one week before loading and transport in basal conditions (control samples), one week later immediately before loading (pre-samples) and again after transport and unloading (about 3 to 4 h) in each new horse box, within 30 min of their arrival at the breeding stations (post-samples). Compared to the before-transport values, increases in circulating T3, T4 and fT4 levels (P < 0.01) were observed after transport, irrespective of breed, but not for fT3 levels. Lower T4 and fT4 levels were observed in basal II (at 1100 h) (P < 0.01) than in basal I (at 0800 h) conditions and before transport. Thoroughbreds showed higher fT3 (P < 0.05) and fT4 (P < 0.01) levels after transport than crossbred stallions. No significant differences were observed for T3 and T4. Compared to the before-transport values, significant increases in rectal temperature (P < 0.01) and HR (P < 0.05) were observed after transport. No differences were observed between basal I, II and before values for functional variables. Significant correlations between T3 and rectal temperature, BW and HR were found. The results indicate that short road transport induces a preferential release of T3, T4 and fT4 hormones from the thyroid gland in relation to different breed, and an increase in rectal temperature and HR. No significant changes in BW were observed. No differences were observed in relation to different ages. The data obtained suggest that the stallion's thyroid hormones and functional variables may play an important role in assessing the effects of transport stress and a horse's coping strategy.