Adrenal steroids stimulate thiazide-sensitive nacl transport by the
rat renal distal tubule.
Vel[acute]azquez, Heino, Ann Bartiss, Paul Bernstein, David H.
Ellison.
Yale University School of Medicine, New Haven, CT and VA Medical
Center, West Haven, CT
APStracts 2:0147F, 1995.
The current experiments were designed to test the hypothesis that
adrenal steroids increase thiazide-sensitive Na and Cl transport by
the mammalian renal distal convoluted tubule (DCT). Male Sprague
-Dawley rats were adrenalectomized and received steroid hormones by
osmotic pumps. Six groups of animals were studied: I, no hormones;
II, replacement levels of dexamethasone only; III, replacement levels
of aldosterone only; IV, replacement levels of both hormones; V;
replacement levels of aldosterone and high levels of dexamethasone;
and VI, replacement levels of dexamethasone and high levels of
aldosterone. Circulating levels of both hormones were found to be in
the high physiological range when infused at the high rate. In vivo
microperfusion of distal tubules was performed to determine rates of
Na and Cl transport. Chlorothiazide was used to assess the magnitude
of electroneutral Na-Cl cotransport. Both aldosterone and
dexamethasone stimulated thiazide-sensitive Na and Cl transport by
the distal tubule by more than 5 fold. [3H]metolazone binding was
measured to assess the number of thiazide-sensitive Na-Cl
cotransporters in renal cortex. Each steroid also increased the
number of [3H]metolazone binding sites in kidney cortex more than 3
fold. The results are consistent with the presence of both
mineralocorticoid and glucocorticoid receptors in the mammalian DCT.
Physiological changes in circulating levels of adrenal steroids may
affect renal NaCl excretion in part by regulating the rate of
electroneutral Na-Cl absorption by the DCT.
Received 21 April 1995; accepted in final form 7 August 1995.
APS Manuscript Number F128-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 August 1995.