Regulation of extrarenal potassium homeostasis by adrenal hormones in rat

The effect of chronic (7-10 days) adrenal insufficiency on extrarenal potassium tolerance was examined by infusing potassium into rats after acute nephrectomy. The increment in plasma potassium concentration was significantly higher in glucocorticoid-replaced adrenalectomized rats versus controls (max ΔP(K) 3.59 ± 0.11 vs. 2.93 ± 0.98 meq/liter; P<0.001). The impairment in extrarenal potassium tolerance in adrenalectomized rats could not be attributed to acidemia, hypotension, changes in plasma insulin or glucose concentration, or potassium retention prior to study. Acute replacement with aldosterone resulted in significant improvement in the rise in plasma potassium after KCl (max ΔP(K) 3.18 ± 0.06 meq/liter; P<0.005 compared with aldosterone-deficient adrenalectomized rats but higher than in controls, P<0.02). If given on a chronic basis, aldosterone replacement led to a complete correction of the defect (max ΔP(K) = 2.89 ± 0.08 meq/liter). Acute epinephrine replacement in adrenalectomized rats also returned potassium tolerance to normal (max ΔP(K) = 0.30.2 ± 0.10 meq/liter). The results demonstrate that extrarenal potassium tolerance is impaired in chronic adrenal insufficiency and suggest that both aldosterone and epinephrine deficiency may contribute to the defect, since replacement with either hormones returns potassium tolerance toward normal. Accordingly, both aldosterone and epinephrine have important extrarenal mechanisms of action.