Effects of adrenalectomy and chronic adrenal corticosteroid replacement on potassium transport in rat kidney.
AUTOR(ES)
Stanton, B
RESUMO
Clearance experiments were carried out in pair-fed rats to examine the long-term effects of adrenalectomy and selective adrenal corticosteroid replacement in physiological amounts on renal potassium transport. To this end, clearance studies were conducted in rats that were sham operated, or adrenalectomized (ADX). ADX animals were given either vehicle, aldosterone (0.5 microgram/100 g body wt per day), dexamethasone (1.2 micrograms/100 g body wt per day), or aldosterone and dexamethasone, by osmotic minipump for 7-9 d whereupon clearance experiments were conducted. After chronic hormone treatment, during basal conditions when only Ringers solution was infused, all groups excreted similar amounts of potassium. However, in all ADX animals without mineralocorticoid replacement, the maintenance of urinary potassium excretion at control levels was associated with hyperkalemia, increased urine flow, and natriuresis; all are factors known to stimulate urinary potassium excretion. During acute potassium infusion, the increase in urinary potassium excretion was less in ADX rats than in controls. This functional deficiency in potassium excretion was partially corrected by dexamethasone and was uniformly associated with a significant increase in urine flow. Aldosterone replacement or aldosterone and dexamethasone given together chronically, sharply increased potassium excretion but did not restore excretion to control levels. Only acute aldosterone infusion (0.2 microgram/100 g body wt bolus plus 0.2 microgram/100 g body wt per hour), superimposed upon chronic aldosterone and dexamethasone treatment, fully restored potassium excretion to control levels. This aldosterone induced enhancement of potassium excretion, both chronic and acute, was not associated with hyperkalemia, and increased urine flow or natriuresis. Thus, physiological levels of both classes of adrenal corticosteroids stimulate renal potassium excretion albeit by different mechanisms. Mineralocorticoids stimulate tubular potassium excretion directly, whereas glucocorticoids augment excretion indirectly by increasing fluid and sodium delivery along the distal nephron.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=425461Documentos Relacionados
- Independent effects of aldosterone and potassium on induction of potassium adaptation in rat kidney.
- Regulation by adrenal corticosteroids of sodium and potassium transport in loop of Henle and distal tubule of rat kidney.
- Differential acute effects of aldosterone, dexamethasone, and hyperkalemia on distal tubular potassium secretion in the rat kidney.
- Localization of Tamm-Horsfall glycoprotein in the normal rat kidney and the effect of adrenalectomy on its localization in the hamster and rat kidney.
- Potassium transport by the isolated perfused kidney.
