An extrarenal mechanism of potassium adaptation.

Rats fed a diet high in potassium for several days survive an acute load of potassium that is lethal to animals on a regular diet. Previous data suggested that this survival occurred because of enhanced kaluresis. Although increased urinary excretion may occur, the major mechanism of this potassium adaptation phenomenon has been found to be extrarenal. Despite nephrectomy just before study, rats previously fed a high potassium diet maintained lower plasma potassium concentrations for at least 2 hr after an acute potassium load than did rats fed a regular diet. Prior adrenalectomy abolished adaptation. Furthermore, rats fed a low sodium diet as an alternative stimulus to aldosterone secretion demonstrated adaptation to potassium loading, as did adrenalecomized rats given large doses of deoxycorticosterone for several days. Adrenalectomy just before the test load of potassium did not abolish adaptation nor did a large dose of aldosterone at that time reproduce it. These data indicate that adaptation is dependent on a chronic increase in aldosterone secretion. The extra potassium removed from the extracellular fluid by adapted rats was not lost into the gastrointestinal tract. It is concluded that more rapid lowering of plasma potassium after acute potassium loads by adapted rats is due to enhanced uptake of potassium by one or more tissues stimulated by chronic aldosteronism.