ILOPROST - INTRACELLULAR CA2-DEPENDENT CONTRACTILE EFFECT ON ISOLATEDSMOOTH-MUSCLE CELLS FROM GUINEA-PIG ILEUM()

Prostaglandin E(2) (PGE(2)) and iloprost induced a concentration-depen dent contraction of smooth muscle cells isolated from the circular lay er of guinea-pig ileum. PGE(2)- and iloprost-induced contractions were inhibited by the selective EP(1)-receptor antagonist, SC19220 (1-acet yl-2-(8-chloro-10, 11-dihydrodibenz (b,f) (1,4) oxazepine-10-carbonyl) -hydrazine), indicating the involvement of the EP(1) subtype of the PG E(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 intr acellular store, the contractile effect of PGE(2) and iloprost was inh ibited. In contrast, incubation of cells in Ca2+-free medium, Ca2+-fre e medium plus EGTA, or in the presence of nifedipine, an organic Ca2+- channel blocker, did not alter the PGE(2)- and iloprost-induced contra ction. These observations suggest that the myogenic effect of PGE(2) a nd iloprost on intestinal smooth muscle is dependent on the release of intracellular calcium.