Prostaglandins activate phosphoinositide metabolism in rat aorta

The ability of the five prostaglandins to activate phosphoinositide (PI) metabolism and to induce contraction was studied in rat aorta. All prostaglandins (PG) tested (B2, D2, E2, F1 alpha and F2 alpha) stimulated PI hydrolysis in the range of 0.01-1,000 microM (EC50 s from 0.9 to 47 microM) and elicited contractions in the range of 0.1-100 microM (EC50 s from 0.3 to 22.1 microM). The rank order potency was PGD2 greater than F2 alpha greater than F1 alpha greater than E2 greater than B2 for PI hydrolysis and PGB2 greater than F2 alpha greater than D2 greater than E2 greater than F1 alpha for contraction. The activation of PI hydrolysis by the various prostaglandins was greater than or equal to the effect of 5-hydroxytryptamine, norepinephrine, angiotensin II and [Arg8]vasopressin. The PI hydrolytic activity of PGD2, E2 and F2 alpha correlated with their ability to induce contraction. The results with PGB2 and F1 alpha showed, however, that activation of PI hydrolysis per se is not always a sufficient or necessary condition for rat aortic contraction.