CONCENTRATION-DEPENDENT EFFECTS OF INSULIN ON CA2-MUSCLE CELLS OF NORMOTENSIVE AND SPONTANEOUSLY HYPERTENSIVE RATS( INFLUX IN VASCULAR SMOOTH)

1. The effect of insulin on cytosolic free Ca2+ concentration was meas ured using fura-2 in vascular smooth muscle cells of normotensive and spontaneously hypertensive rats. 2. In both strains, insulin increased cytosolic free Ca2+ concentration in a concentration range between 10 (-6) and 10(-3) units/ml. The maximum increase in cytosolic free Ca2concentration was observed with 10(-5) units/ml insulin (107 +/- 25 an d 82 +/- 27 nmol/l in spontaneously hypertensive rats and normotensive rats, respectively). 3. The effect of insulin was dependent on extrac ellular Ca2+ and was enhanced by stimulation of protein kinase C. 4. T hus insulin appears to induce a Ca2+ influx in vascular smooth muscle cells only over a certain range of concentrations. No significant diff erence in the response to insulin of cells from normotensive and hyper tensive rats was observed.