ILOPROST - INTRACELLULAR CA2+-DEPENDENT CONTRACTILE EFFECT ON ISOLATED SMOOTH-MUSCLE CELLS FROM GUINEA-PIG ILEUM

Prostaglandin E(2) (PGE(2)) and iloprost induced a concentration-dependent contraction of smooth muscle cells isolated from the circular layer of guinea-pig ileum. PGE(2)- and iloprost-induced contractions were inhibited by the selective EP(1)-receptor antagonist, SC19220 (1-acetyl-2-(8-chloro-10, 11-dihydrodibenz (b,f) (1,4) oxazepine-10-carbonyl)-hydrazine), indicating the involvement of the EP(1) subtype of the PGE(2) receptor. When cells were incubated for 10 min in the presence of strontium (4 mM L(-1)), an inhibitor of the release of Ca2+ from intracellular store, the contractile effect of PGE(2) and iloprost was inhibited. In contrast, incubation of cells in Ca2+-free medium, Ca2+-free medium plus EGTA, or in the presence of nifedipine, an organic Ca2+-channel blocker, did not alter the PGE(2)- and iloprost-induced contraction. These observations suggest that the myogenic effect of PGE(2) and iloprost on intestinal smooth muscle is dependent on the release of intracellular calcium.