THE ACTION OF THE PEPTIDOLEUKOTRIENE LTD(4) ON INTRACELLULAR CALCIUM IN RAT MESANGIAL CELLS

The dose-dependent effect of CGP 45715A on the LTD(4)-induced Ca2+ res ponse of glomerular mesangial cells has been studied. Our results demo nstrate that the LTD(4)-dependent increase in the cytosolic Ca2+ conce ntration primarily involves an InsP(3)-mediated release of Ca2+ from i ntracellular storage sites and to a minor extent an enhanced influx of Ca2+ through receptor-operated Ca2+ channels located in the plasma me mbrane. The action of CGP 45715A on the Ca2+ response is an inhibitory one and is convincingly explained by a displacement of LTD(4) from it s receptor site(s). The contractile effect of LTD(4) on pulmonary smoo th muscle is proposed to be mainly caused by a receptor-mediated hydro lysis of phosphatidylinoaitol-4 5-bisphosphate.