Fecal corticosterone reflects serum corticosterone in Florida sandhill cranes

Florida sandhill cranes (Grus canadensis pratensis) were conditioned to confinement 6 hr/day for 7 days. On day 8, each bird's jugular vein was catheterized, blood samples were drawn, and each crane was confined for 6 hr. Using a randomized, restricted cross-over design, cranes were injected intravenously with either 0.9% NaCl solution or ACTH (cosyntropin; Cortrosyn; 0.25 mg). During the 6 hr of confinement, fecal samples (feces and urine) were collected from each of five cranes immediately after defecation. Individual fecal samples were collected approximately at hourly intervals and assayed for corticosterone. We showed previously that serum corticosterone did not vary significantly following saline injection, but peaked significantly 60 min after ACTH injection. Maximal fecal corticosterone concentrations (ng/g) were greater (P < 0.10; median 1087 ng/g) following ACTH stimulation compared to maximal fecal corticosterone concentrations at the end of acclimation (day 7; median 176) and following saline treatment (median 541). In cranes under controlled conditions, fecal corticosterone concentration reflects serum corticosterone levels, fecal corticosterone, Grus canadensis pratensis, sandhill cranes, serum corticosterone levels.     

Brain histamine-plasma corticosterone interactions

Significant elevation in plasma corticosterone of rats achieved by intraperitoneal (i.p.) administration of corticosterone (2.4 mg/kg) was associated with a rapid (2.5 min) and significant increase in hypothalamic histamine (HA) levels which persisted for 60 min. Midbrain and cortical HA concentrations were not affected. Significant and prolonged elevation of hypothalamic, midbrain and cortical HA levels was achieved by L-histidine administration (500 mg/kg i.p.). The most significant increase was noted in the hypothalamus and persisted for 10 hours. The elevated brain HA levels were associated with significant increase in plasma corticosterone levels which lasted for 120 mins. Present data supports the involvement of central HA in endocrine function.     

The effect of transdermal corticosterone application on plasma corticosterone levels in pregnant Lacerta vivipara

Relationships between hormones and behaviour can be explored by altering endogenous hormone levels, often through implantation of silastic tubing or osmotic pumps filled with a hormone or its agonists or antagonists. However, organisms in sensitive life-history stages (such as pregnancy) may be adversely affected by the surgical procedures associated with these manipulations, necessitating use of non-invasive techniques. We demonstrate that the application of a sesame oil-corticosterone mixture to the skin of pregnant female common lizards (Lacerta vivipara) elevates plasma levels of the hormone. Pregnant female L. vivipara were captured and treated daily for 1-20 days with the sesame oil-corticosterone mixture (experimental group) or with vehicle only (control group). Blood samples were collected and analyzed for corticosterone by radioimmunoassay. Baseline plasma corticosterone levels were elevated within 1 h in the experimental group. Similar levels ( approximately 145 ng/ml) were found over the subsequent 2 days, and by day 5 had risen significantly higher ( approximately 281.9 ng/ml), where they remained for the duration of the experiment. These increases are comparable to those found in other species using related techniques. No significant changes in plasma corticosterone levels occurred in the control group. Finally, corticosterone levels also were determined for untreated females that were captured, held overnight, sampled, and released to access to the natural range of basal corticosterone levels. Basal plasma levels of corticosterone in pregnant females varied among individuals independently of female body size or corpulence.     

A radioimmunoassay for plasma corticosterone

A radioimmunoassay for plasma corticosterone has been developed. Antiserum against corticosterone was produced in rabbits immunized with corticosterone -21- hemisuccinate conjugated to bovine serum albumin. The assay was practical and reliable. The coefficient of variation between assays was ± 23% and among assays was ± 8%. Plasma corticosterone of mice is measured readily by assaying directly aliquots of a methylene chloride extract of 40 μl of plasma. The mean plasma corticosterone concentration of mice was similar to that obtained by other methods.     

Dexamethasone and corticosterone receptor sites

Summary High resolution light microscopic autoradiography was used, together with regional surveys and combined aeridine orange staining, to define in rat hippocampus cellular and subcellular sites of concentration and retention of ³H dexamethasone and to compare the topographic pattern of labeling with that of ³H corticosterone. Nuclear uptake of ³H dexamethasone in the hippocampus is demonstrated for the first time in vivo. With ³H dexamethasone, strongest nuclear radioactive labeling was observed in certain glial cells throughout the hippocampus, followed by strong nuclear labeling in most neurons in area CA1 and in the adjacent dorsolateral subiculum and weak nuclear labeling in granule cells of the dentate gyrus. Neurons in areas CA2, CA3, CA4, and in the dorsomedial subiculum and indusium griseum showed little or no nuclear labeling after ³H dexamethasone. With ³H corticosterone, strongest nuclear labeling was observed in neurons in area CA2 and in the dorsomedial subiculum and indusium griseum, followed by area CA1, then CA3 and CA4; the dentate gyrus contained scattered strongly labeled cells among cells with intermediate nuclear labeling. At the subcellular level, evidence for both nuclear and cytoplasmic accumulation of label was found. The results indicate that dexamethasone and corticosterone have both nuclear and cytoplasmic binding sites and that particular patterns of target cell distribution exist, characteristic for each agent. This suggests a differential regulation of cellular functions for the two compounds. Corticosterone nuclear binding appears to be more extensive and encompasses regions with dexamethasone binding. Whether in certain of these common regions corticosterone binds to the same receptor as dexamethasone, which seems possible, or to different receptors, remains to be clarified.     

Exogenous and endogenous corticosterone in feathers

In birds, the steroid hormone corticosterone (CORT) increases in response to real or perceived threats to homeostasis. A long‐term record of CORT exposure is recorded in feathers when the hormone is incorporated into the keratinized tissue, and then preserved when the mature feather is cut off from the blood supply. The opportunity to retrospectively assess the exposure of an individual to stressors by measuring the amount of CORT in a feather has generated excitement amongst avian ecologists. However, this technique is relatively new and requires additional validations. In this study, we performed experiments in wild caught European starlings Sturnus vulgaris to test whether: 1) CORT deposition in the feather depends on time of day and 2) whether an ecologically relevant stressor (unpredictable food access) causes a change in feather CORT. We found that exogenous CORT was incorporated into feathers during the day and the night. However, there was no difference in feather CORT between birds with unpredictable access to food and those with continuous access, indicating that feather CORT might not always detect ecologically relevant stressors.     

Short-term fasting affects locomotor activity,corticosterone, and corticosterone binding globulin in a migratory songbird

Unpredictable events such as severe storms lead to an increase in circulating corticosterone (CORT) in breeding birds. This increase is often accompanied by elevations in foraging and irruptive behavior. We were interested in determining if acute food restriction (such as might occur during inclement weather) is a sufficient cue to elicit an increase in locomotor activity, increase CORT secretion, and/or decrease circulating levels of corticosterone binding globulin (CBG) in white-crowned sparrows (Zonotrichia leucophrys gambelii). Male Z.l. gambelii were housed individually in environmental chambers on long days (LD 20:4) to simulate breeding season daylength. Birds were fed ad libitum, and on select days, food was removed 2 h after lights on (fasted treatment), or was removed and replaced (control). We analyzed CORT and CBG levels after 1, 2, 6, 22 (lights on), and 23 h under fasted and control conditions. We also measured activity during the 23-h experiment. Activity levels were increased under fasted conditions during the daytime relative to control conditions, but activity levels did not differ between treatments during the night. Fasting as little as 1, 2, and 6 h significantly increased total CORT levels above baseline (control), although after 22 h, total CORT levels under fasted conditions matched those under control conditions. Plasma CBG decreased after the 22-h fast, and remained low after the 23-h fast. This change was sufficient to significantly elevate free CORT levels in fasted birds relative to ad libitum food conditions, despite the lack of difference in total CORT levels.     

Japanese quail selected for high plasma corticosterone response deposit high levels of corticosterone in their eggs

Poor habitat quality or body condition often correlates with high responsiveness of the hypothalamo-pituitary-adrenal (HPA) axis rather than with elevated baseline levels of glucocorticoids. We hypothesized that, for egg-laying vertebrates, high responsiveness of the HPA axis would correspond to high concentrations of corticosterone in yolk. We tested the prediction that Japanese quail (Coturnix coturnix japonica) selected for high plasma corticosterone response to brief immobilization (HS quail) would lay eggs with higher yolk corticosterone concentrations than birds selected for low response (LS quail). Quail from both lines were left undisturbed, outside of the stressors associated with daily management, before a first round of egg collection. In a second experiment, quail of both lines were experimentally stressed during the week before egg collection. In both cases we found quail from the HS line to lay eggs with significantly higher yolk corticosterone concentrations than quail of the LS line. After exposure to added experimental stressors, the line difference was more pronounced (increasing from 62% to 96%). There was no line difference in concentrations of yolk testosterone. Our results suggest that (1) genetic differences underly differences in the transfer of maternal corticosterone to yolk and (2) females may be able to control deposition of corticosterone into yolk through a mechanism independent of baseline corticosterone titers.     

Interaction of testosterone, corticosterone and corticosterone binding globulin in the white-throated sparrow (Zonotrichia albicollis)

Plasma binding globulins bind steroid hormones and are thought to regulate hormone access to tissues. Mammals have both sex steroid binding globulin (SSBG) and corticosteroid binding globulin (CBG). Birds, however, have no detectable SSBG, leading to the early conclusion that birds have no plasma regulation of sex steroids. CBG, however, can bind androgens with relatively high affinity. In birds, therefore, the control of androgenic effects may be tightly regulated by glucocorticoid physiology because glucocorticoids compete with androgens for CBG binding sites. We report levels of total testosterone (T), total corticosterone, CBG, and estimated free T in the males, the more aggressive morph had higher levels of total T; female morphs did not differ. Approximately 96% of T was bound to CBG, but a lack of morph or sex-specific differences in corticosterone titers or CBG capacity caused patterns of free T to mirror those of total T. While CBG has the potential to greatly influence T availability to tissues, in this species interactions between T, CBG and corticosterone do not appear to alter general patterns of T availability to tissues.     

Plasma corticosterone concentrations in the perinatal rat

1. Plasma corticosterone concentrations were determined in the foetal rat during the gestational period from day 18·5 to term and in postnatal rats over the first few hours after delivery. 2. The plasma corticosterone concentrations in foetal rats are as high as six times maternal values at day 19 of gestation and are approximately equal to maternal values from day 20 to term. 3. In postnatal rats the plasma corticosterone concentrations rise 3·5-fold on average within 5hr. of delivery. 4. The results are discussed in relation to the function of adrenal steroids in postnatal liver development.     

Exogenous and endogenous corticosterone alter feather quality

We investigated how exogenous and endogenous glucocorticoids affect feather replacement in European starlings (Sturnus vulgaris) after approximately 56% of flight feathers were removed. We hypothesized that corticosterone would retard feather regrowth and decrease feather quality. After feather regrowth began, birds were treated with exogenous corticosterone or sham implants, or endogenous corticosterone by applying psychological or physical (food restriction) stressors. Exogenous corticosterone had no impact on feather length and vane area, but rectrices were lighter than controls. Exogenous corticosterone also decreased inter-barb distance for all feathers and increased barbule number for secondaries and rectrices. Although exogenous corticosterone had no affect on rachis tensile strength and stiffness, barbicel hooking strength was reduced. Finally, exogenous corticosterone did not alter the ability of Bacillus licheniformis to degrade feathers or affect the number of feathers that failed to regrow. In contrast, endogenous corticosterone via food restriction resulted in greater inter-barb distances in primaries and secondaries, and acute and chronic stress resulted in greater inter-barb distances in rectrices. Food-restricted birds had significantly fewer barbules in primaries than chronic stress birds and weaker feathers compared to controls. We conclude that, although exogenous and endogenous corticosterone had slightly different effects, some flight feathers grown in the presence of high circulating corticosterone are lighter, potentially weaker, and with altered feather micro-structure.     

Features of ginseng saponin-induced corticosterone secretion.

Ginseng saponin administered intraperitoneally to rats induced a significant rise in plasma corticosterone, while it tended to increase plasma glucose and to decrease plasma immunoreactive insulin. Oral or intraperitoneal administration of ginseng saponin increased plasma corticosterone in unanesthetized, pentobarbital-anesthetized or alloxan-diabetes rats. The histamine-induced rise in plasma corticosterone was suppressed by pretreatment with diphenhydramine, whereas the ginseng-induced rise was not. Ginseng saponin decreased rectal temperature while it increased plasma corticosterone. Ginseng-induced corticosterone secretion was superimposed on the basal levels of plasma corticosterone due to fasting and circadian rhythm. Thus ginseng saponin would be a kind of stressful agent and have different features associated with the stimulation of the pituitary-adrenocortical system from several other chemical agents.     

A radioimmunoassay for human plasma corticosterone.

A radioimmunoassay for human plasma corticosterone has been developed. Antiserum against corticosterone was produced in rabbits immunized with corticosterone-21-hemisuccinate conjugated to bovine serum albumin. The antiserum cross-reacted with progesterone, DOC and dehydrocorticosterone more than 20%. After the extraction with ether, and the separation by Sephadex LH-20 microcolumn chromatography, recovery was 51.2 +/- 12.1% in 50 assays. The mean coefficient of variation between assays was 7.7% and within assays was 8.6%. Human plasma corticosterone is measured readily by assaying aliquots of an ether extract of 0.05 to 0.1 ml of plasma after microcolumn chromatography. The mean plasma corticosterone concentration at 9 a.m. was 7.1 +/- 3.2 ng/ml in 45 normal subjects. Plasma corticosterone increased 5.2 times as much as basal values after ACTH injection, whereas radioimmunoassayed cortisol increased 2.4 times. On the other hand, plasma corticosterone decreased to 22.6% of basal values at four hours after 1 mg dexamethasone, whereas radioimmunoassayed cortisol decreased to 12.3% of basal values.     

Circadian rhythm of corticosterone in diabetic rats

We proposed that the circadian rhythm of corticosterone in diabetic rats would have a different pattern than that in non-diabetic control rats. To test this hypothesis, 20 male Sprague-Dawley rats were given ad libitum access to a stock diet and housed individually in a light and temperature controlled room. Ten rats were made diabetic by two subcutaneous injections of streptozotocin. Ten rats which were not injected served as controls. Thirteen days after induction of the diabetes, tail blood samples were taken every 4 h for 24 h. Plasma corticosterone levels were significantly higher in diabetic rats than in control rats at 3 time points during the light cycle; however, concentrations were similar during the dark cycle. We speculate that diabetes may cause alterations in the steroid feedback mechanism to the hypothalamus and/or pituitary, resulting in an abnormal circadian rhythm of plasma corticosterone.