Suppression of renin secretion by insulin: dependence on extracellular calcium

The isolated perfused rat kidney was used to examine the effect of insulin on renin release (RR). Insulin produced a dose-dependent reduction of RR when added to the perfusate at concentrations between 10 and 1,000 microU/ml. When kidneys were perfused with a calcium-free perfusate, RR increased nearly fivefold. Insulin (1,000 microU/ml) not only failed to suppress RR in calcium-free perfusions but stimulated it. The addition of verapamil (10(-5) M) to the perfusate likewise prevented the insulin inhibition of RR. Perfusion without potassium reduced RR to one-third of control values. The addition of insulin to kidneys perfused without potassium further suppresses RR. We conclude that at concentrations similar to those found in plasma, insulin modulates renin secretion. This process requires the influx of calcium possibly through insulin receptor-operated channels.