Plasma aldosterone levels after KCl loading in rats adapted to a high potassium diet.

Plasma levels of aldosterone, corticosterone, potassium and renin activity, and urinary potassium excretion, were measured in control (CK) rats, and in rats adapted to a high potassium diet (HK), before and after an acute intragastric KCl load. Prior to the KCl load there was no difference in plasma potassium (K) or plasma aldosterone. Following the KCl load, HK rats maintained a lower plasma K, and, except at 30 min after the load, a lower plasma aldosterone than CK rats. At a low plasma K there was no difference in plasma aldosterone between CK and HK rats. At a high plasma K (greater than 8 mmol/l) the HK rats had a higher plasma aldosterone for the same plasma K than CK rats. The enhanced ability to excrete an acute K load seen in HK rats seems unlikely to be due to higher levels of plasma aldosterone.