In this study we investigated the role of corticosterone (B) in regulating the proportion of laying females, timing of breeding, reproductive output (egg size and number), and yolk precursor levels in chronically B-treated female zebra finches (Taeniopygia guttata). Corticosterone treatment via silastic implant elevated plasma B to high physiological (stress-induced) levels (24.1 +/- 5.3 ng/ml ...

Exogenous administration of glucocorticoids is a widely used and efficient tool to investigate the effects of elevated concentrations of these hormones in field studies. Because the effects of corticosterone are dose and duration-dependent, the exact course of plasma corticosterone levels after exogenous administration needs to be known. We tested the performance of self-degradable corticostero...

The corticosterone response to capture and handling was measured in free-living red-eared slider turtles, Trachemys scripta elegans. To determine the ability of this species to exhibit this endocrine response, slider turtles were bled at the time of removal from hoop nets and again at 30 and 60 min following capture to create plasma profiles of acute corticosterone secretion from individuals. P...

The mineralocorticoid activity of corticosterone based on acute changes in urinary Na+/K+ ratios in adrenalectomized rats was 1000 times less than that of aldosterone. However, corticosterone had only kaliuretic actions whereas aldosterone had both antinatriuretic and kaliuretic properties. Corticosterone inhibited the antinatriuretic actions of aldosterone. Adrenalectomized rats infused contin...

This study demonstrates the changes in six different pathophysiological parameters such as body weight, body temperature, fecal pellet count, blood-brain barrier (BBB) permeability, plasma corticosterone level and emergence of hemorrhagic peptic ulcer spots due to exposure to high environmental heat in three different age groups of freely moving rats. Methods: Each age group of rats was sub di...

Stress-induced increases in neonatal corticosterone demonstrate a unique shift from ACTH independence to ACTH dependence between postnatal day 2 (PD2) and day 8 (PD8) in newborn rats. This shift could be due to the binding of a bioactive, non--immunoreactive plasma ligand to the adrenocortical melanocortin 2 receptor (MC2R) (ACTH receptor). A potent MC2R antagonist would be useful to evaluate t...

Very small amounts of adrenocorticosteroids are synthesized by brain tissue in vitro. While there is evidence suggesting that the synthesis of aldosterone in the brain may have a role in the hypertension of the Dahl salt-sensitive rat, the de novo synthesis of aldosterone or corticosterone within the brain of a living animal has not been demonstrated. We have used sensitive ELISAs to measure al...

Deficiencies in the conversion between active and inactive glucocorticoids in the kidney can lead to hypertension. However, the significance of glucocorticoid metabolism in specific kidney regions in vivo is not clear, possibly in part due to the difficulty in measuring glucocorticoid levels in kidney regions in vivo. We used microdialysis techniques to sample renal interstitial fluid from cons...

11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1) intracellularly regenerates active corticosterone from circulating inert 11-dehydrocorticosterone (11-DHC) in specific tissues. The hippocampus is a brain structure particularly vulnerable to glucocorticoid neurotoxicity with aging. In intact hippocampal cells in culture, 11beta-HSD-1 acts as a functional 11beta-reductase reactivating in...

A sensitive protein-binding assay has been used to measure plasma concentrations of total corticosterone during postnatal development in the rat. These concentrations were extremely low on days 6--12, showed a significant rise by day 14, and then continued to rise until peaking on day 24. Plasma titers of corticosteroid-binding globulin rose even more dramatically from day 12 onward. Consequent...