[Effect of insulin on contractile response and calcium binding in rat aorta]

Insulin affects physiological mechanisms involved in blood pressure regulation, and at the cellular level modifies endothelial and vascular smooth muscle functions underlying the changes in peripheral resistance. We describe the effects of preincubation with insulin (40 microU/ml for 1-2 hs) on the contractile reactivity of intact rat aortic rings and on 45Ca2+ uptake of EGTA-hyperpermeabilized rat aortic segments. Preincubation with insulin did not affect either contractions induced by 1 microM of NA, or their relaxation induced by 10 mM of caffeine. The contractile response to 1 microM of Ang-II (which in rat aorta is endothelium-independent) was stimulated by insulin preincubation resulting in increases of both maximal developed force and velocity of its spontaneous relaxation. The difference in 45Ca2+ uptake between insulin-treated and insulin-untreated aortic segments was greater at 5 minutes than it was at 30 minutes.

Insulin preincubation affects directly the mechanical response of Ang-II stimulated aortic smooth muscle; we suggest that the modification of SR function is one of the mechanisms involved in insulin regulation of cytosolic Ca2+.