NATRIURETIC AND KALIURETIC RESPONSE TO POTASSIUM LOAD - MODULATION BYSODIUM-INTAKE

Potassium (K) loading is followed by a rapid increase in sodium (Na) a nd K excretion. To evaluate the influence of Na intake on this effect, we studied the acute natriuretic and kaliuretic response to a single oral K load (100 mmol) in six healthy volunteers equilibrated on a 10- , 100-, and 400-mmol Na intake. Compared to the 100-mmol Na intake, th e 400-mmol Na intake greatly enhanced the natriuretic effect of the K load; during the 10-mmol Na intake no natriuresis but even some Na ret ention occurred. The kaliuretic effect was not significantly changed a nd occurred at similar values of plasma K. Plasma aldosterone was supp ressed during the 400-mmol Na diet and stimulated during the 10-mmol N a diet, but the relative increments after the Kcl load did not differ among the three diets. In conclusion, whereas the effect of a K load o n kaliuresis is relatively independent of Na intake, its effect on Na excretion varies from marked natriuresis to slight Na retention. The N a retention is probably due to acute K-induced aldosterone stimulation , and the natriuresis to K-induced increase in distal Na delivery not utilized to promote K excretion. Apparently, the integration of renal Na and K handling after a K load is such that K balance is maintained at the cost of Na balance.