Atrial natriuretic factor: localization in the adrenal gland of the lizard Podarcis sicula and effects on pituitary-adrenal axis activity

The occurrence of atrial natriuretic factor (ANF) immunoreactivity was investigated in the adrenal gland of the lizard Podarcis sicula by avidin-biotinylated peroxidase complex (ABC) immunocytochemical technique: ANF immunoreactivity was present in the chromaffin tissue, and was absent in the steroidogenic tissue. The role of ANF in the modulation of the pituitary-adrenal axis activity was investigated in vivo by intraperitoneal administration of ANF. The effects were evaluated by examination of the morphological and morphometrical features of the tissues, as well as the plasma levels of adrenocorticotropic hormone (ACTH), corticosterone, aldosterone, norepinephrine, and epinephrine. ANF (28 microg/100 g body wt) did not affect ACTH plasma levels, that remained almost unchanged; in contrast, corticosterone plasma levels increased from 6.45 +/- 0.070 ng/ml in carrier-injected lizards to 9.69 +/- 0.080 ng/ml 24 h after the injection; aldosterone levels decreased from 2.19 +/- 0.010 ng/ml in carrier-injected specimens to 0.58 +/- 0.003 ng/ml 24 h after the experimental treatment. In the chromaffin tissue, an increase in the number of epinephrine cells and a decrease in the number of norepinephrine cells were observed, decreasing the numeric norepinephrine/epinephrine cell ratio, from 1.4/1 of control specimens to 0.3/1 24 h after ANF administration. Moreover, norepinephrine plasma levels decreased from 998 +/- 4.600 pg/ml in carrier-injected specimens to 321 +/- 2.230 pg/ml 24 h after ANF administration; epinephrine plasma levels were elevated from 614 +/- 3.410 pg/ml in carrier-injected specimens to 1672 +/- 10.800 pg/ml 24 h after the experimental treatment. The presence of ANF in the adrenal gland suggests that, also in reptiles as in other vertebrates, this peptide, locally released from the chromaffin cells, may modulate the activity of the adrenal gland, probably in a paracrine manner. The effects of ANF on the adrenal gland suggest that this peptide may affect reptilian salt and fluid homeostasis.     

Neuropeptide Y modulates pituitary-adrenal axis activity in the lizard, Podarcis sicula

The role of neuropeptide Y (NPY) in the modulation of the pituitary-adrenal axis activity in a lizard, Podarcis sicula, was investigated by in vivo NPY administration. The effects were evaluated by examination of the morphological and morphometrical features of the tissues as well as the plasma levels of ACTH, corticosterone, aldosterone, norepinephrine, and epinephrine. Intraperitoneally administered NPY (27 nmol /100g body wt) raised ACTH plasma levels (from 5.23+/-0.06 pg/ml in carrier injected specimens to 6.83+/-0.01 pg/ml, 24 h after the injection). In the steroidogenic cells a strong decrease of lipid amount was found; corticosterone plasma level increased from 6.28+/-0.02 ng/ml in carrier injected lizards to 7.96+/-0.01 ng/ml 24 h after the injection); aldosterone levels were raised from 1.88+/-0.02 ng/ml in carrier injected specimens to 6.38+/-0.05 ng/ml 24 h after the experimental treatment. In the chromaffin tissue, an increase in the number of epinephrine cells and a decrease in the number of norepinephrine cells were observed, decreasing the numeric norepinephrine/epinephrine (NE/E) cell ratio, from 1.4/1 of control specimens to 0.5/1 24 h after NPY administration. Moreover, norepinephrine plasma level were elevated from 922+/-4.30 pg/ml in carrier injected specimens to 3075+/-11.30 pg/ml 24 h after NPY administration; epinephrine plasma level increased from 502+/-2.40 pg/ml in carrier injected specimens to 2759+/-8.70 pg/ml 24 h after the experimental treatment. Consistent with these findings, morphological observations showed many chromaffin cells weakly stained and with a reduced content of secretory granules. These results suggest that, in P. sicula, NPY may play a role in the modulation of the pituitary-adrenal axis activity. Previous studies localized NPY in the epinephrine cells of P. sicula adrenal gland; taken together, these results suggest that this peptide might participate in the regulation of adrenal gland activity, enhancing corticosteroid and catecholamine secretion in a paracrine/autocrine manner. The mechanism of action of NPY is discussed.     

Effects of dopamine on the adrenal gland of Podarcis sicula (Reptilia, Lacertidae)

The effects of dopamine administration on the adrenal gland of a lizard, Podarcis sicula, are described. Dopamine (0.7mg/100g body wt/day for 4 consecutive days) raised plasma ACTH and corticosterone levels (ACTH: from the basal level of 4.40+/-0.05-7.30+/-0.08pg/ml 24h after the fourth dopamine injection; corticosterone: from 3.59+/-0.03ng/ml in untreated lizards to 7.40+/-0.05ng/ml 24h after the fourth dopamine injection), showing a stimulatory effect on the pituitary-interrenal axis activity. In the chromaffin tissue dopamine apparently enhanced the activity of PNMT enzyme; in fact a strong raise in the number of adrenaline cells and a decrease in the number of noradrenaline cells were observed, decreasing the numeric NA/A cell ratio, from 1.4/1 of control specimens to 0.5/1 24h after the fourth dopamine injection. At EM level, chromaffin cells contained both NA and A granules, as well as very clear granules (CG); CG granules showed granular elements ranging between 340 and 347A in diameter. These cells might be the morphological expression of a process of catecholamine resynthesis, due to a possible increase in catecholamine release, following exposure to dopamine.     

Influence of stress on adrenocortical function in the male tree shrew (Tupaia belangeri)

Adrenocortical function in the tree shrew (Tupaia belangeri) was evaluated by reference to levels of individual corticosteroids as an initial phase in the clarification of the hormonal mechanisms by which stress influences male reproductive function. Corticosteroids were separated with Sephadex LH-20 chromatography and measured by specific radioimmunoassay procedures. Corticosterone was the principal corticosteroid in the peripheral plasma and in unstressed animals the ratio corticosterone:cortisol was 4.5:1 (1000 hr samples). Basal levels of corticosterone and cortisol exhibited parallel diurnal fluctuations with a peak at 0600 hr preceding the onset of daily activity and similar to that described for other diurnally active species. Levels of corticosterone and cortisol were markedly elevated 10 min after either restraint stress applied at various times during the day or ACTH administration to both saline- and dexamethasone-pretreated animals. In each of these experimental situations cortisol showed a greater relative increase from basal levels as compared to corticosterone resulting in a decline in the ratio corticosterone:cortisol. For example, the unstressed ratio of corticosterone (9.1 +/- 0.8 ng/ml) and cortisol (2.0 +/- 0.2 ng/ml) at 1000 hr was 4.5:1. Following 10 min of restraint stress the ratio declined to 1.5:1 (corticosterone, 44.9 +/- 1.4 ng/ml; cortisol, 31.7 +/- 1.3 ng/ml). An increase in cortisol is considered to be an important component of the physiological response to stress by the tree shrew adrenal. It is concluded that the adrenal cortex of the tree shrew normally produces corticosteroids through two pathways and the secretion of both corticosterone and cortisol are responsive to acute ACTH stimulation and feedback inhibition by dexamethasone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of fecal glucocorticoids in the North Atlantic right whale (Eubalaena glacialis)

Very little is known about the endocrinology of the baleen whales. The highly endangered North Atlantic right whale (NARW; Eubalaena glacialis) is a good model species, because most NARW individuals are photo-identified with known histories. We used an 125I corticosterone assay, shown to reliably measure cortisol metabolites, to determine glucocorticoid metabolite concentrations in 177 NARW fecal samples collected between 1999-2004 in the Bay of Fundy, Canada. Fecal glucocorticoid metabolite concentrations varied significantly with sex and reproductive category, being highest in pregnant females (mean +/-SE: 238.14+/-74.37 ng/g) and mature males (71.6+/-11.36), intermediate in lactating females (39.33+/-5.82), and lower in non-reproducing females (23.11+/-4.25) and immature males (34.33+/-5.01) and females (14.0+/-0.41). One case also suggests that glucocorticoids rise markedly in response to severe entanglement in fishing lines. Whales with fecal glucocorticoid content over 100 ng/g (termed "high-cort" samples) were rare, and included most pregnant females, some mature males, a fatally entangled whale, and several very young animals. Glucocorticoid concentrations were highly correlated with androgen concentrations in males and pregnant females. We analyzed the elution profiles of glucocorticoid and androgen metabolites in 13 samples with high-performance liquid chromatography (HPLC) to determine the extent to which androgen metabolites cross-react with our glucocorticoid assay. Males, pregnant females, non-pregnant females, and "high-cort" whales each had distinctly different immunoreactive HPLC profiles of glucocorticoid and androgen metabolites. A major glucocorticoid metabolite was prominent in all "high-cort" whales including the fatally entangled whale. The major fecal androgen was not testosterone but was instead a more nonpolar steroid (possibly dihydrotestosterone), which may be diagnostic of males. Androgen metabolites showed only minor cross-reactivity to our glucocorticoid assay, having a slight influence on glucocorticoid results in particular individuals. We conclude that fecal glucocorticoid analysis appears to be a useful measure of adrenal activity and reproductive condition for NARW.     

Effect of single doses of dexamethasone and adrenocorticotrop hormone on serum bone markers in healthy subjects and in patients with adrenal incidentalomas and Cushing's syndrome

The aim of the present study was to explore whether short-term changes in glucocorticoid activity which occur during dynamic testing of the pituitary adrenal axis with dexamethasone, ACTH, or metyrapone could have an effect on serum osteocalcin (OC) and beta-crosslaps (beta-CTx) concentrations in healthy subjects, in patients with adrenal incidentalomas and in those with Cushing's syndrome. The study included 40 healthy subjects (35 women and 5 men, age range 18-69 yr), 49 patients with adrenal incidentalomas (34 women and 15 men, age range 19-77 yr) and 8 patients with Cushing's syndrome (5 cortisol-producing adenomas and 3 pituitary-dependent Cushing's syndrome, 3 women and 5 men, age range 19-70 yr). Serum OC and beta-CTx concentrations were determined with electrochemoluminescent immunoassays at midnight, after an overnight fast between 08:00 and 09:00 h, after an overnight dexamethasone test (1 mg, orally) and after a single dose of metyrapone (30 mg/kg, orally). In healthy subjects and in patients with adrenal incidentalomas, serum bone marker concentrations were also measured after a single dose of ACTH injection (Cortrosyn depot, 1 mg im). Patients with Cushing's syndrome, but not those with adrenal incidentalomas, showed significantly lower serum OC at midnight (18.5+/-12 ng/ml, mean+/-SD) and between 08:00 and 09:00 h (17.7+/-9.6 ng/ml) compared to corresponding values obtained in healthy subjects (24.5+/-7.0 and 28.3+/-12.2 ng/ml, respectively). Serum OC concentrations were significantly decreased after a single dose of 1-mg dexamethasone in healthy subjects (from 28.3+/-12.2 to 21.8+/-9.5 ng/ml) and in patients with adrenal incidentalomas (from 29.8+/-15.9 to 24.1+/-14.1 ng/ml), whereas serum OC concentrations remained unchanged in patients with Cushing's syndrome. In addition, serum OC concentrations were even more markedly decreased after a single dose of ACTH injection in both healthy subjects (12.5+/-4.6 ng/ml) and in patients with adrenal incidentalomas (12.2+/-6.5 ng/ml). By contrast, metyrapone administration failed to induce significant changes in OC levels. There were no significant differences in beta-CTx concentrations between the three groups or after drug treatments. Thus, serum OC levels should be interpreted with caution when obtained during testing of the pituitary-adrenal axis with dexamethasone or ACTH.     

Diminished diurnal secretion of adrenocorticotropin (ACTH), but not corticosterone, in old male rats: possible relation to increased adrenal sensitivity to ACTH in vivo

The diurnal secretion of ACTH and corticosterone was examined in chronically cannulated young (3-4 months old), middle-aged (10-12 months old), and old (22-24 months old) Fischer 344 male rats. Plasma corticosterone in young rats increased from baseline concentrations of 78 +/- 5 to a maximum of 171 +/- 24 ng/ml at 1730 h and declined to basal levels by 1930 h. Middle-aged and old rats demonstrated a similar magnitude and time course of corticosterone release. However, comparison of the relative concentrations of ACTH released during the diurnal surge revealed that old rats secreted 35% less ACTH than young or middle-aged animals (P less than 0.05). Age-related changes in the sensitivity of the adrenal gland to a submaximal dose of ACTH were tested in dexamethasone-pretreated animals at 1100 and 1700 h in a separate experiment. Plasma corticosterone levels were significantly greater after ACTH administration (1 mIU/kg ACTHAR, iv) at 1700 h in both young and old rats compared to 1100 h values (P less than 0.05), and levels 20 min post-ACTH injection at 1700 h were significantly greater in old than young or middle-aged rats at the same time (P less than 0.05). These results demonstrate that 1) there are no age-related changes in the diurnal secretion of corticosterone in Fischer 344 male rats; 2) there is a decline in the peak level of ACTH during the diurnal surge of old compared to young animals; and 3) adrenal sensitivity to ACTH at 1700 h is greater in old compared to young or middle-aged rats. We hypothesize that the greater increase in adrenal sensitivity to ACTH is responsible for the maintenance of the corticosterone rhythm in the presence of diminished ACTH concentrations in older rats.     

Noninvasive fecal monitoring of glucocorticoids in spotted hyenas, Crocuta crocuta.

The aim of this study was to validate a method for measuring glucocorticoids noninvasively in feces of spotted hyenas (Crocuta crocuta). Three established enzyme immunoassays (EIA) for cortisol, corticosterone, and 11-oxoetiocholanolone were tested, but proved unsatisfactory. A new EIA using another corticosterone antibody was established and was used for all subsequent analyses; this EIA was validated by demonstrating parallelism between serial dilutions of spotted hyena fecal extracts and dilutions of standard corticosterone and by the recovery of corticosterone added to fecal extracts. High-performance liquid chromatography (HPLC) fractions analyzed by EIA showed various immunoreactive substances with polarities of unconjugated steroids. The physiological relevance of fecal glucocorticoid metabolites was further validated by demonstrating that (1) injection of exogenous ACTH to four males and two females led to a significant increase in fecal glucocorticoid metabolites within 24-50 h, (2) the translocation of a male spotted hyena to a new enclosure resulted in a fivefold increase compared to baseline concentrations, and (3) agonistic social interactions and physical conflict resulted in large increases of fecal glucocorticoid metabolites in both protagonists. Fecal steroid assessment is therefore of use in monitoring adrenal activity in spotted hyenas.     

A generalized fecal glucocorticoid assay for use in a diverse array of nondomestic mammalian and avian species

Noninvasive fecal glucocorticoid analysis has tremendous potential as a means of assessing stress associated with environmental disturbance in wildlife. However, interspecific variation in excreted glucocorticoid metabolites requires careful selection of the antibody used in their quantification. We compared four antibodies for detecting the major fecal cortisol metabolites in yellow baboons following (3)H cortisol administration, ACTH challenge, and HPLC separation of fecal glucocorticoid metabolites. The most effective antibody (ICN corticosterone RIA; Cat. No. 07-120102) demonstrated relatively high cross-reactivities to the major cortisol metabolites present in feces during peak excretion, following both radiolabel infusion and ACTH challenge. This same antibody also detected increased fecal glucocorticoid metabolites after ACTH administration in the African elephant, black rhinoceros, Roosevelt elk, gerenuk, scimitar-horned oryx, Alaskan sea otter, Malayan sun bear, cheetah, clouded leopard, longtailed macaque, and northern spotted owl. Results suggest that (1) fecal glucocorticoid assays reliably detect endogenous changes in adrenal activity of a diverse array of species and (2) where comparisons were made, the ICN corticosterone antibody generally was superior to other antibodies for measuring glucocorticoid metabolites in feces.     

Regulation of 18-hydroxydeoxycorticosterone in the rat.

Simultaneous measurements of plasma 18-hydroxydeoxycorticosterone (18 OH-DOC), corticosterone, and aldosterone were performed in the rat by using RIA. Under basal conditions, 18 OH-DOC levels averaged 11.3 +/- 3.7 (SE) ng/ml. Plasma concentrations were increased 8-fold (86.8 +/- 8.0 ng/ml) 1 h after 1 U sc ACTH. Dexamethasone suppressed 18 OH-DOC to less than 1.5 ng/ml, irrespective of Na+ intake. Neither Na+ depletion nor Na+ loading had any influence on 18 OH-DOC levels. Excellent correlation between 18 OH-DOC and corticosterone (r = 0.90, P less than 0.001) was observed, whereas there was none between 18 OH-DOC and aldosterone (r = 0.061, P greater than 0.6). In the rat, 18 OH-DOC is an ACTH-dependent steroid which does not appear to be under the influence of the renin-angiotensin system.     

Ultradian, circadian and seasonal rhythms in cortisol secretion and adrenal responsiveness to ACTH and yarding in unrestrained red deer (Cervus elaphus) stags.

Seasonal changes in the activity and responsiveness of the adrenal gland in red deer (Cervus elaphus) stags were quantified by measuring 24 h endogenous cortisol secretory profiles and plasma cortisol responses to either administration of exogenous ACTH or a standardised stressor during November (period of velvet growth), February (pre-rut), April (mid-rut) and July (post-rut) (southern hemisphere) using a remote blood sampling device (DracPac). Ultradian rhythms in the concentration of plasma cortisol were observed resulting from the episodic secretion of cortisol from the adrenal cortex at a mean rate of 0.8 pulses/h. Circadian rhythms in plasma cortisol concentrations were also found in 11 out of the 20 complete 24 h profiles (mean amplitude, 3.8+/-1.4 ng/ml). Seasonal rhythms in mean 24 h plasma cortisol concentrations and cortisol pulse parameters were also observed. Mean 24 h plasma cortisol concentrations were higher in November (12.5+/-1.0 ng/ml) than in February (6.3+/-1.0 ng/ml), April (4.0+/-1.0 ng/ml) or July (4.2+/-1. 0 ng/ml). Cortisol pulse height, nadir and amplitude were all significantly higher in November than at other times of the year (P<0.01). Peak cortisol concentrations following infusion of ACTH(1-24) (0.04 IU kg(-1)) were higher (P<0.05) in November (55.8+/-2.7 ng/ml) and lower (P<0.001) in April (33.7+/-1.8 ng/ml) than those in February and July (48.7+/-2.0 ng/ml and 45.4+/-2.0 ng/ml respectively). The area under the cortisol response curve was significantly smaller (P<0.05) in April (266.6+/-15.3 ng/ml/190 min) than at other times of the year (February, 366.1+/-15.3 ng/ml/190 min; July, 340.7+/-15.3 ng/ml/190 min and November, 387.8+/-21.2 ng/ml/190 min). These data demonstrate that the adrenal gland of the red deer stag exhibits ultradian, circadian and seasonal rhythms in activity, and that its responsiveness to ACTH varies with season. November, a period of reproductive quiescence in the southern hemisphere, with new antler growth and rapid weight gain, is associated with higher mean plasma cortisol concentrations and a greater responsiveness to exogenous ACTH. In contrast, the breeding season is associated with lower adrenal activity and responsiveness.     

Physiological stress in captive Greater rheas (Rhea americana): Highly sensitive plasma corticosterone response to an ACTH challenge

Up to the present no studies have been conducted either on baseline concentrations of adrenal hormones or on hormonal responses to stress in Greater rhea (Rhea americana) and most ratite species. The aims of this work were to assess the presence of corticosterone in plasma of Greater rhea, to validate a corticosterone ¹²⁵I-radioimmunoassay for determining corticosterone levels in plasma samples and to study the activation of the adrenal gland after an adrenocorticotrophic hormone (ACTH) challenge. Six captive Greater rhea juveniles of 10 months of age received an intravenous ACTH injection. Blood samples were taken at 0 min (baseline pre-ACTH levels), and post-injection at 15, 30, 60 min and at 24 and 48 h. The high pressure liquid chromatography (HPLC) analysis of pooled plasma showed that corticosterone is the glucocorticoid found in the plasma of Greater rhea. Biochemical assays of standard validation (e.g., parallelism, exogenous corticosterone recovery) showed that measurements of corticosterone present in the plasma of the Greater rhea provided by commercial corticosterone ¹²⁵I-radioimmunoassay were accurate and precise. ACTH challenge induced a more than 40-fold increase in plasma corticosterone at 60 min post-ACTH (from 4.0 to 166.5 ng/ml, on average). The corticosterone response to ACTH in Greater rhea was higher than is usual in birds, an apparently typical characteristic of ratites.     

Postnatal overexpression of insulin-like growth factor II in transgenic mice is associated with adrenocortical hyperplasia and enhanced steroidogenesis

The influence of postnatal insulin-like growth factor II (IGF-II) overexpression on adrenal growth and function was investigated in 3-month-old male phosphoenolpyruvate carboxykinase (PEPCK) promoter human IGF-II transgenic mice, which are characterized by 4-to 6-fold elevated postnatal IGF-II serum levels. Plasma corticosterone levels of PEPCK-IGF-II transgenic mice were 2-fold higher than in age- and sex-matched controls, both in the morning (7.4 +/- 1.5 vs. 17.8 +/- 3.9 ng/ml, P < 0.01) and in the evening (33.3 +/- 6.5 vs. 65.3 +/- 12 ng/ml, P < 0.01). When PEPCK-IGF-II transgenic mice were subjected to an ACTH challenge, corticosterone levels were stimulated 6-fold, to 396 +/- 17 ng/ml after 60 min, compared with 230 +/- 24 ng/ml in the control group. In contrast to corticosterone, plasma ACTH levels were similar in transgenic and control mice, excluding an indirect effect of IGF-II at the hypothalamic or pituitary level. In vitro, the basal and ACTH-induced corticosterone production of adrenal glands from transgenic mice was higher (2-fold and 1.8-fold, respectively) than that of control organs. However, when normalized for adrenal weight, the in vitro corticosterone secretion was similar in both groups. At autopsy, adrenal weights of transgenic mice were significantly greater than those of control adrenal glands (3.3 +/- 0.2 vs. 2.0 +/- 0.2 mg, P < 0.01, n = 10). Furthermore, a local expression of human IGF-II could be demonstrated in transgenic adrenal glands by RT-PCR, whereas in normal adult mice, no adrenal expression of IGF-II was detected. Stereological investigation of adrenal glands from another set of PEPCK-IGF-II transgenic mice and controls (6-month-old males) demonstrated that the increase in adrenal weight in transgenic mice is mainly caused by a 50% increase in the number of zona fasciculata cells, whereas cell volume and zonation of transgenic adrenal glands remained unchanged. In conclusion, our data indicate that postnatal overexpression of IGF-II induces an increased adrenal weight and elevated corticosterone serum levels, presumably by a direct mitogenic effect of IGF-II on adrenocortical fasciculata cells.     

Handling during pregnancy in the blue fox (Alopex lagopus): the influence on the fetal pituitary-adrenal axis

Previous studies revealed that handling is a stressor for farmed blue foxes. The present study was designed to examine the effects of a 1-min daily handling stress applied to pregnant blue fox vixens on the function of the fetal pituitary-adrenal system. Plasma concentrations of adrenocorticotropin hormone (ACTH), cortisol, and progesterone, adrenal content of cortisol and progesterone, in vitro adrenal production of these steroids and response to ACTH, and adrenal weights were measured in control (C; n = 73) and stressed (S; n = 58) fetuses. The ACTH levels were lower in stressed fetuses than in the controls (C: males, 128.6 +/- 6.1 pg/ml; females, 165.9 +/- 6.1 pg/ml; S: males, 122.3 +/- 5.4 pg/ml; females, 145.0 +/- 8.1 pg/ml; P < 0.05). In contrast, increased plasma cortisol concentrations in both sexes were demonstrated in stressed compared with control fetuses (C: males, 9.2 +/- 0.4 ng/ml; females, 9.2 +/- 0.4 ng/ml; S: males, 11.8 +/- 0.7 ng/ml; females, 13.2 +/- 0.7 ng/ml; P < 0.00001). The same difference was observed in plasma progesterone concentrations (C: males, 1.54 +/- 0.07 ng/ml; females, 1.49 +/- 0.10 ng/ml; S: males, 1.86 +/- 0.11 ng/ml; females, 1.74 +/- 0.10 ng/ml; P < 0.01). Prenatal stress did not change the baseline adrenal production of cortisol but prevented the cortisol response to ACTH in female fetuses and decreased the progesterone production in both sexes. Additionally, prenatally stressed fetuses of both sexes had significantly lower adrenal weights than controls (C: males, 9.4 +/- 0.3 mg; females, 9.5 +/- 0.4 mg; S: males, 8.1 +/- 0.3 mg; females, 8.2 +/- 0.4 mg; P < 0.001). These results indicate that prenatal handling stress induces a dysregulation of the pituitary-adrenal axis in the fetus and suggest that increased plasma glucocorticoids in the stressed dam can cross the placenta and influence the fetal hypothalamicpituitary-adrenal axis.     

Fecal glucocorticoid metabolites as a measure of adrenal activity in dairy cattle

The feasibility of monitoring acute adrenal activity in New Zealand dairy cattle by measuring fecal glucocorticoid metabolites was investigated. Fecal glucocorticoid measurement has potential as an indicator of adrenal activity and animal stress because sampling is relatively noninvasive, does not interfere with the stress response itself, and permits on-farm monitoring. Fecal samples were collected from dairy cattle following ACTH challenge and exposure to stressors (novel environment, transport). Two immunoassays (11,17-dioxoandrostane enzymeimmunoassay and ICN corticosterone radioimmunoassay) were compared. Both assays detected increased immunoreactive fecal glucocorticoid metabolites following acute adrenal activity and the temporal relationship between plasma corticosteroids and fecal metabolite excretion was determined. The time to peak excretion was closely related to the transit time of digesta passing between the bile duct and the rectum and was affected by seasonal changes in feed intake and pasture digestibility. We conclude that measurement of glucocorticoid metabolites reliably indicates acute adrenal activity in dairy cattle and in combination with other physiological and behavioral measures has potential for monitoring health and welfare in dairy cattle. (c) 2002 Elsevier Science (USA).     

alpha-Melanocyte-stimulating hormone and adrenocorticotropin in the regulation of glucocorticoid secretion during the perinatal period in sheep.

To determine the role of other ACTH-like peptides in the regulation of glucocorticoid secretion in fetal sheep, we examined the responses of the adrenal gland of fetal and newborn sheep to comparable single doses of alpha MSH (75 micrograms) or ACTH (50 micrograms) during the last third of gestation and the first month of postnatal life. alpha MSH first increased the plasma glucocorticoid concentration at 121--130 days of gestation [from 16 +/- 1.5 to 36.9 +/- 9 (SE) ng/ml]; the response to alpha MSH persisted on days 131--140 of gestation and during the first month after birth. ACTH first increased the plasma glucocorticoid concentration at 131--140 days of gestation and increased it further in the first month after birth (from 18.9 +/- 3.6 to 97.0 +/- 10 ng/ml). The observations that the adrenal glands of fetuses and newborn lambs responded to alpha MSH at a dose comparable to that of ACTH and that the response to alpha MSH in the fetus preceded the response to ACTH may indicate that adrenal receptors mature during fetal development. These data also suggest that the regulation of the adrenal during fetal life may involve more than one tropic hormone.     

Adrenocortical function in a prototherian mammal, Tachyglossus aculeatus (Shaw).

The peripheral plasma concentrations and production rates of corticosterone and cortisol were measured in the conscious, unrestrained echidna (Tachyglossus aculeatus) under basal conditions and during maximal ACTH stimulation. Using Sephadex LH-20 column chromatography and radioligand assay, only cortisol and corticosterone could be detected in the peripheral blood plasma at very low concentrations of 0-07 +/- 0-03 (S.E.M.) mug/100 ml and 0-14 +/- 0-07 mug/100 ml respectively. Two-hourly sampling over periods of 36-48 h disclosed a diurnal periodicity in the combined plasma concentration of these corticosteroids, the high concentrations corresponding to periods of behavioural activity. Marked, short-term fluctuations in plasma corticosteroid concentration were also observed during periods of more frequent (20 min) sampling. Constant rate i.v. infusion of synthetic ACTH increased the plasma concentrations of both steroids to maximal values of 0-42 +/- 0-23 mug cortisol/100 ml and 1-06 +/- 0-56 mug corticosterone/100 ml at infusion rates of 1 i.u. ACTH/kg/h. This is approximately 1/160 of the potency of this ACTH in man. The production rates of corticosterone and cortisol, measured by isotope dilution during constant rate i.v. infusion of 3H-labelled tracers, were only 0-35 +/- 0-21 and 0-56 +/- 0-26 mug/kg/h respectively during saline infusion, and increased to 2-86 +/- 3-47 and 2-74 +/- 2-07 mug/kg/h during the infusion of 1 i.u. ACTH/kg/h. The metabolic clearance rate of cortisol was greater than that of corticosterone and both were depressed by ACTH. Plasma corticosteroid concentrations were increased after surgery during ether anaesthesia and in sick animals with heavy worm infestation. It is concluded that the adrenal cortex of echidnas responds to ACTH stimulation and stress in a similar way to eutherians, but the level of activity is much lower.     

Variability in leptin and adrenal response in juvenile Steller sea lions (Eumetopias jubatus) to adrenocorticotropic hormone (ACTH) in different seasons

Eight free-ranging juvenile Steller sea lions (SSL; 6 males, 2 females; 14-20 months) temporarily held under ambient conditions at the Alaska SeaLife Center were physiologically challenged through exogenous administration of adrenocorticotropic hormone (ACTH). Four individuals (3 males, 1 female) underwent ACTH challenge in each of two seasons, summer and winter. Following ACTH injection serial blood and fecal samples were collected for up to 3 and 96 h, respectively. A radioimmunoassay (RIA) was validated for leptin, and using a previously validated RIA for cortisol, collected sera were analyzed for both cortisol and leptin. ACTH injection resulted in a 2.9-fold increase (P=0.164) in leptin which preceded a 3.2-fold increase (P=0.0290) in cortisol by 105 min in summer. In winter, a 1.7-fold increase in leptin (P=0.020) preceded a 2.1-fold increase (P=0.001) in serum cortisol by 45 min. Mean fecal corticosteroid maxima were 10.4 and 16.7-fold above baseline 28 and 12 h post-injection and returned to baseline 52 and 32 h post-injection, in summer and winter, respectively. Data indicate acute activity in juvenile adrenal glands is detectable in feces approximately 12-24 h post-stimulus in either season, with a duration of approximately 40 h in summer and 20 h in winter. Changes in serum cortisol proved statistically significant both seasons and elevated concentrations were detected by 30 min post-stimulus (baseline 64.8+/-4.2; peak 209.5+/-18.3 ng/ml: summer; baseline 87.0+/-15.7; peak 237.6+/-10.0 ng/ml: winter), whereas the changes that occurred in serum leptin proved to be significant only in winter (baseline 6.4+/-0.6; peak 18.7+/-7.0 ng/ml: summer; baseline 4.2+/-0.5; peak 7.5+/-0.6 ng/ml: winter). Changes in fecal corticosteroids proved significant only in summer (baseline 117.8+/-36.7; peak 1219.3+/-298.4 ng/g, P=0.038: summer; baseline 71.8+/-13.7; peak 1198.6+/-369.9 ng/g, P=0.053: winter) due to a high degree of individual variability in winter months. The data indicate that ACTH stimulates leptin production earlier than cortisol in both summer and winter, and that while the leptin response appears most variable in summer, fecal corticosteroids are most variable in winter.