Inositol-1,4,5-trisphosphate releases calcium from skinned cultured smooth muscle cells

Abstract

We examined the effects of inositol-1,4,5-trisphosphate on 45Ca uptake and 45Ca efflux in the saponin skinned primary cultured rat aortic smooth muscle cells. 10 μM inositol-1,4,5-trisphosphate induced a rapid (half time<10 sec) and large quantity of Ca release in both 45Ca uptake and 45Ca efflux in the skinned cells preloaded with 1 μM free Ca. Dose response curves showed that 100 μM inositol-1,4,5-trisphosphate produced a maximal Ca release of 97.3% of the MgATP dependent 45Ca uptake or 289 μ moles/liter cells, which was much greater than the maximal caffeine induced Ca release and would be sufficient to produce maximal tension.