Plasma K plus and insulin: changes during KCl infusion in normal and nephrectomized dogs

Potassium chloride was administered by constant, intravenous infusion in splenectomized, but otherwise normal, dogs. The concentration of potassium, [K+], and of insulin, [insulin], in the arterial plasma was measured at frequent intervals. To assess the relative contributions of extrarenal and renal mechanisms toward the maintenance of normal plasma [K+], the results were compared with data obtained previously in splenectomized, nephrectomized dogs. During the infusion, plasma [K+] increased in the dogs with kidneys intact at a mean rate slightly less than that in the nephrectomized dogs. After the infusion was stopped, plasma [K+] declined to about 0.75 meq/liter above control values in both groups of animals. The results indicate the operation of both renal and extrarenal homoeostatic mechanisms. The renal mechanisms contributed measurably during the infusion of KCl, but not immediately after the infusion was stopped. Simultaneous measurements of plasma [K+] and plasma [insulin] indicate that insulin may be involved in the extrarenal homeostatic response.