Potassium homeostasis during hyperinsulinemia: Effect of insulin level, β-blockade, and age

The euglycemia glucose clamp technique was used to evaluate the influence of level and duration of hyperinsulinemia, presence of β-adrenergic blockade, and subject age on insulin-mediated changes in plasma potassium. In 16 young subjects, 2-h insulin infusions at 20 (n = 6), 80 (n = 13), and 200 (n = 8) mU.m^-2.min^-1 resulted in dose-dependent declines in plasma potassium (P < 0.001 at all doses) during the 1st h. During the 2nd h plasma potassium declined during the 20 mU.m^-2.min^-1 infusions, was stable during the 80 mU.m^-2.min^-1 infusions, and rose slightly during the 200 mU.m^-2.min^-1 infusions. There was a significant reciprocal relationship between the changes in plasma potassium during the 1st and 2nd h of study (r = 0.99, P < 0.01). During 4-h infusions (80 mU.m^-2.min^-1, n = 6) plasma potassium declined during the first 90 min (p < 0.001) and rose thereafter until the end of the infusion (P < 0.05). Studies with and without propranolol infusion at two insulin dose levels (20 and 80 mU.m^-2.min^-1) in six young subjects showed no effect of β-blockade, and studies at three insulin dose levels [20 (n = 5), 80 (n = 6), and 200 (n = 6) mU.m^-2.min^-1 in 10 older males (63-77 yr)] showed no effect of age on the changes in plasma potassium during hyperinsulinemia. These results suggest the presence of a regulatory mechanism influencing insulin-mediated alterations in plasma potassium. This mechanism appears uninfluenced by age of β-adrenergic blockade.