VERAPAMIL DEPRESSES THE SYNTHESIS OF LIPOXYGENASE PRODUCTS BY HYPOXIC CARDIAC RAT FIBROBLASTS IN CULTURE

Lipoxygenase metaboolites of arachidonic acid are potent chemotactic and vasoconstrictive agents and their local production in the myocardium induces the migratioon of polymorphonuclear cells into ischemic myocardium. These cells have been shown to play a role in the development of ischemic myocardial lesions. In the present study, the synthesis of arachidonic acid lipoxygenase metabolites by rat cardiac cells in culture and the effect of verapamil were investigated under normal and hypoxic conditions. Myocytes and fibroblasts metabolized exogenous arachidonic acid into 12-HETE and an unidentified metabolite (X). Fibroblasts synthesized significantly greater amounts of 12-HETE than myocytes (P < 0.01). Hypoxia (glucose-free medium and low PO2) and veapamil (10-7 M) under normal conditions, did not change metabolite synthesis by either type of cells. Under hypoxia, verapamil decreased significantly 12-HETE and X production by fibroblasts (P < 0.01 and P < 0.05), whereas the synthesis in myocytes was not changed. It is concluded that the decrease in lipoxygenase product synthesis under hypoxia by verapamil may contribute to its therapeutic effects on the ischemic heart.