THE EFFECTS OF ADRENAL STEROIDS AND POTASSIUM DEPLETION ON THE ELABORATION OF AN OSMOTICALLY CONCENTRATED URINE*

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Abstract
Administration of deoxycortico-sterone acetate (DCA) (1.0 mg/kg/day for 6 to 24 days) to dogs on a high NaCl intake resulted in reduction of maximum osmotic U/P ratios at low urine flows in the hydropenic state. During mannitol diuresis and vasopressin infusion, the amount of solute- free water reabsorption (TCH2O) was significantly decreased. At urine flow rates above 5 ml/minute, the urine was frequently hypotonic. The slope of osmolal clearance on urine flow was significantly less (mean 0.777) than in control animals (0.994). These changes were vasopressin-resistant. Plasma K levels were reduced, indicating K deficiency. Discontinuation of DCA and administration of KOH supplements showed that the observed alterations were reversible. Hydrocortisone (7.5 mg/kg/day and 10.0 mg/kg/day for periods of 6 to 13 days) did not significantly decrease maximum osmolar U/P ratios, TCH2O or the slope relating Cosm (osmolal clearance to urine flow. "This steroid also did not reduce the plasma K level in dogs on a high NaCl intake." The data obtained have been interpreted to indicate a diminished permeability of the renal epithelium of the distal tubules and collecting ducts to water after DCA and K depletion.

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