Effect of insulin on renal potassium metabolism

The effect of insulin on renal potassium excretion was examined by employing the euglycemic insulin clamp technique in combination with renal clearance measurements. While euglycemia was maintained, insulin was infused at rates of 4.8 (n = 7) and 12 (n = 5) mU·kg^-1·min^-1. Steady-state plasma insulin levels of 164 ± 8 and 370 ± 15 μU/ml were achieved in the low- and high-dose studies, respectively. Base-line plasma potassium concentration declined progressively by a mean of 0.14 ± 0.09 (P < 0.05) and 0.40 ± 0.05 meq/liter (P < 0.01) during the low- and high-dose insulin infusion protocols. Urinary potassium excretion did not change significantly from base line with either insulin dose. Because the decline in plasma potassium concentration could have masked a stimulatory effect of insulin on U(K)V, six rats received a 12-mU·kg^-1·min^-1 euglycemic insulin clamp in combination with an exogenous potassium infusion to maintain the plasma potassium concentration constant at the basal level (4.03 ± 0.03 vs. 4.05 ± 0.05 meq/l). Under these conditions of normokalemia, insulin augmented U(K)V 2.4-fold, from 0.20 ± 0.05 to 0.48 ± 0.04 meq/l (P < 0.001).