1. Potassium infusion causes an increase in immunoreactive insulin levels in dogs, but either a small (30%) or no increase in humans. Since insulin stimulates the uptake of K+ by cells, a regulatory role for K+-induced insulin release has been postulated. To study the role of insulin in regulating cellular K+ uptake, six fasting normal volunteer subjects underwent two K+ infusions on separate days. Both infusions delivered 0.6 mmol h−1 kg−1 for 3 h. In one subject glucose was simultaneously infused at 0.67 mmol h−1 kg−1 (a rate known to increase peripheral insulin levels by 40–100%); the other infusion contained no glucose.
2. Plasma insulin levels did not increase during the glucose-free infusions. During glucose-containing infusions, insulin levels were 40% higher than those during glucose-free infusions. Despite this, neither urinary potassium excretion nor the increment in plasma K+ concentration or the calculated cellular K+ uptake differed significantly during the 3 h of glucose-free and glucose-containing infusions respectively.
3. These data do not support the view that potassium-induced insulin secretion regulates cellular potassium uptake within the physiological range of plasma K+ concentration.