Differential regulation of adrenal corticosteroids after restriction-induced drinking in rats

Abstract

Wotus, Cheryl, and William C. Engeland. Differential regulation of adrenal corticosteroids after restriction-induced drinking in rats. Am J Physiol Regul Integr Comp Physiol 284: R183-R191, 2003. First published October 3, 2002 10.1152/ajpregu.00027.2002.-Water-restricted rats exhibit a rapid decrease in plasma corticosterone after drinking. The present study examined the effect of restriction-induced drinking on plasma aldosterone and plasma clearance of corticosterone. Rats were water restricted for 6-7 days and then killed before or 15 min after water administration; plasma and adrenal hormones were assayed. Plasma and adrenal corticosterone decreased after drinking without a change in plasma corticosteroid-binding globulin; plasma ACTH decreased or did not change. In contrast, plasma aldosterone did not change or increased after drinking; plasma renin activity was elevated by water restriction and increased further after drinking. In another experiment, rats were adrenalectomized, and corticosterone and aldosterone were replaced with pellets and osmotic minipumps, respectively. Rats were water restricted and killed. There was a small decrease in plasma corticosterone but no change in aldosterone after drinking in adrenalectomized animals. These data suggest that changes in plasma steroids after restriction-induced drinking result from zone-specific responses of the adrenal to known secretagogues, with minimal contribution from increased plasma clearance.corticosterone; aldosterone; corticosteroid-binding globulin; steroid clearance; dehydration THE RAT ADRENAL CORTEX is divided into two morphologically and functionally distinguishable steroidogenic zones. The inner zona fasciculata/reticularis produces corticosterone in response to its primary secretagogue, ACTH, which is released from the anterior pituitary. The outer zona glomerulosa produces the mineralocorticoid aldosterone in response to multiple factors, including ANG II, an end product of the renin-angiotensin system. Increased secretion of corticosterone and aldosterone represents a homeostatic response to stressful stimuli. In contrast to the response following stress, a marked reduction in plasma and adrenal corticosterone is observed immediately after water is presented to rats restricted to a limited amount of water each day (8,18,24,31,40). Although evidence suggests that this rapid decline in corticosterone may occur though mechanisms acting at the level of the adrenal cortex (8, 40), it is not known whether restriction-induced drinking affects aldosterone in a similar manner. Previous studies have shown increases in plasma aldosterone after deprivation-induced drinking in dogs (37) and sheep (3), whereas there were no changes in plasma aldosterone after drinking in dehydrated humans (15). However, rapid changes in corticosterone and aldosterone after drinking have not been investigated concurrently in the same animal model of dehydration. Moreover, there are inconsistencies concerning the effect of dehydration alone on aldosterone secretion ...

Aldosterone Target Neurons in the Nucleus Tractus Solitarius Drive Sodium Appetite

“…Plasma samples were frozen (-80°C) for subsequent measurement of aldosterone and corticosterone concentrations by radioimmunoassay (RIA), as described by Wotus and Engeland (2003). RIA measurements served as verification that target plasma levels of aldosterone and corticosterone were achieved and that no adrenal tissue remained.…”

Effect of global and regional sympathetic blockade on arterial pressure during water deprivation in conscious rats

“…2002; Alzet, Palo Alto, CA) and cholesterol pellets (Sigma-Aldrich) containing 50% corticosterone (75 mg; Roussel Uclaf, Romaineville, France). Doses were based on a previous protocol, which resulted in plasma concentrations in the physiological range (63). Sham rats received vehicle (propylene glycol; SigmaAldrich) in the minipump and cholesterol-only pellets.…”

“…Because the volume of blood sampled was twice that of the other experiments in this study, the 24-h plasma sample was omitted in this experiment. In addition to the osmolality measurements, some of the plasma was aliquotted and frozen for later analysis of plasma corticosterone and adrenocorticotropic hormone (ACTH) (28,63). At the end of the experiment, body and thymus weights were also collected as physiological indicators of adequate corticosterone replacement (3).…”

“…In the ADx rats, we replaced aldosterone and corticosterone at a constant rate according to past studies (63). Because the ADx rats are unable to increase production of adrenocortical hormones during WD, we reasoned that this would be an effective way to test their role in the cardiovascular response to WD.…”

Modulation of stress responses: How we cope with excess glucocorticoids

“…Plasma ACTH occasionally does decrease slightly during this time, but the adrenal corticosterone response is strikingly inhibited by 15 min (Amhold et al, this issue). Moreover, when corticosterone is replaced in adrenalectomized rats and the water restriction paradigm applied, plasma corticosterone concentrations decrease little, if at all (23). The inhibition of adrenal and plasma corticosterone has been observed as early as 3 and 6 minutes after presentation of water, well before changes in ACTH occur (21).…”