Participation of both intracellular free Ca2+ and protein kinase C in tonic vasoconstriction induced by prostaglandin F2 alpha.

The roles of intracellular free Ca2+ and protein kinase C in the tonic contraction induced by prostaglandin were studied. Prostaglandin F2 alpha induced tonic contraction of rat thoracic aorta in both control and Ca2(+)-free solution. Close correlations were observed between the contractile response of aortic strips and the changes in intracellular free Ca2+ concentration in vascular smooth muscle cells assessed with the fluorescent Ca2+ indicator fura 2, both in control and Ca2(+)-free solutions. Prostaglandin F2 alpha also enhanced the production of inositol 1,4,5-trisphosphate in vascular smooth muscle cells before the rise of the intracellular free Ca2+ concentration. Moreover, 1-(5-isoquinoline-sulfonyl)-2-methylpiperazine, an inhibitor of protein kinase C, inhibited the tonic contractions induced by PGF2 alpha and 12-O-tetradecanoyl phorbol-13-acetate, a direct activator of protein kinase C, at similar concentrations. These results suggest that both intracellular free Ca2+ and protein kinase C participate in prostaglandin F2 alpha-induced tonic contraction.