Glucose uptake in isolated heart cells: studies on the role of insulin.

Glucose transport in cardiac myocytes is highly sensitive to stimulation by insulin. The concentration of half-maximal action (3 X 10(-10) mol/l) corresponds to the high-affinity constant of the insulin receptor. Insulin action on the glucose carrier is exclusively due to an increase in Vmax with no changes in Km. The onset of insulin action is preceded by a lag phase of about 20 s and found to be ATP-dependent. Neither the sodium pump, nor calcium, but magnesium appears to be involved in the mediation of insulin action.