Role of alpha-adrenergic hormones in potassium homeostasis in the rat.

To determine whether alpha-adrenergic stimulation impairs extrarenal potassium disposal in the rat, we studied the effect of an alpha-agonist and antagonist on the rise in plasma potassium concentration produced by a potassium infusion of 3 mEq KCl/kg over a 90-minute period to nephrectomized rats. Compared with KCl alone, the alpha-agonist phenylephrine caused more than a 25% increment in the peak plasma potassium, and reduced the volume of distribution of the potassium load. Addition of the alpha-blocker, phentolamine, to phenylephrine completely abolished the increment in potassium caused by KCl infusion. There were no differences in plasma bicarbonate, arterial pH, or plasma glucose levels among the groups. When an identical protocol was performed in nephrectomized rats also prepared by adrenalectomy, induction of diabetes, and chemical sympathectomy, the rise in plasma potassium level after KCl infusion was again augmented by phenylephrine. Addition of phentolamine also markedly blunted the increment in potassium in this group. These results show that alpha-adrenergics impair extrarenal potassium disposal in the rat. The effect does not depend on endogenous insulin or other potassium-regulatory factors. alpha-Adrenergics appear to play an important role in extrarenal potassium homeostasis.