LACK OF INHIBITION OF GLYCERYL TRINITRATE BY DIPHENYLENEIODONIUM IN BOVINE CORONARY-ARTERY

Recent studies indicate that diphenyleneiodonium is a potent inhibitor of glyceryl trinitrate-induced relaxation in rat aorta precontracted with phenylephrine. We have explored the generality of this action in bovine coronary artery precontracted with the thromboxane A(2) mimetic , 9,11-dideoxy-11 alpha,9 alpha-epoxy-methano-prostglandin F-2 alpha ( U46619). Diphenyleneiodonium 0.3 mu M was without effect (endothelium absent) or caused mild potentiation (0.3 mu M or 10 mu M; endothelium present) of the relaxant response to glyceryl trinitrate. Lack of inhi bition was not due to U46619, since inhibition was still prominent in rat aorta precontracted with this agent. It is concluded that diphenyl eneiodonium distinguishes between cellular mechanisms mediating vasodi lator responses to glyceryl trinitrate in rat aorta and bovine coronar y artery.