EFFECT OF INSULIN ON CONTRACTILE RESPONSE AND CALCIUM CAPTATION IN RAT AORTA

Insulin affects physiological mechanisms involved in blood pressure re gulation, and at the cellular level modifies endothelial and vascular smooth muscle functions underlying the changes in peripheral resistanc e. We describe the effects of preincubation with insulin (40 mu U/ml f or 1-2 hs) on the contractile reactivity of intact rat aortic rings an d on Ca-45(2+) uptake of EGTA-hyperpermeabilized rat aortic segments. Preincubation with insulin did not affect either contractions induced by 1 mu M of NA, or their relaxation induced by 10 mM of caffeine. The contractile response to 1 mu M of Ang-II (which in rat aorta is endot helium-independent) was stimulated by insulin preincubation resulting in increases of both maximal developed force and velocity of its spont aneous relaxation. The difference in Ca-45(2+) uptake between insulin- treated and insulin-untreated aortic segments was greater at 5 minutes than it was at 30 minutes. Conclusions: insulin preincubation affects directly the mechanical response of Ang-ll stimulated aortic smooth m uscle; we suggest that the modification of SR function is one of the m echanisms involved in insulin regulation of cytosolic Ca2+.