Influence of OKY-1581 on responses to arachidonic acid in the feline pulmonary vascular bed.

The effects of OKY-1581, a thromboxane synthesis inhibitor, on pulmonary vascular responses to arachidonic acid (AA) were investigated under baseline and elevated tone conditions in the intact chest cat. Under conditions of controlled blood flow at baseline tone, intralobar injections of AA increased lobar arterial pressure in a dose-related manner. These pressor responses were reduced by OKY-1581, and a small vasodilator response was unmasked.

Pulmonary vasodilator responses to vasoactive intestinal peptide in the cat.

We investigated the effects of vasoactive intestinal peptide (VIP) in the feline pulmonary vascular bed under conditions of controlled pulmonary blood flow when pulmonary vascular tone was at base-line levels and when vascular resistance was elevated. Under base-line conditions, VIP caused small but significant reductions in lobar arterial pressure without affecting left atrial pressure. Decreases in lobar arterial pressure in response to VIP were greater and were dose related when lobar vascular resistance was increased by intralobar infusion of U 46619, a stable prostaglandin endoperoxide analogue.

Influence of cyclooxygenase blockade on responses to isoproterenol, bradykinin and nitroglycerin in the feline pulmonary vascular bed.

We investigated the effect of indomethacin on responses to isoproterenol, bradykinin and nitroglycerin in the feline pulmonary vascular bed when pulmonary vascular resistance was actively increased by infusion of U46619 in order to determine if vasodilator responses to these agents were dependent on the integrity of the cyclooxygenase pathway. Since pulmonary blood flow and left atrial pressure were held constant, changes in lobar arterial pressure directly reflect changes in lobar vascular resistance. Intralobar injections of isoproterenol, bradykinin, and nitroglycerin decreased lobar arterial pressure in a dose-related manner.

Pulmonary vasodilator responses to vagal stimulation and acetylcholine in the cat.

Responses to vagal stimulation and acetylcholine were investigated in the feline pulmonary vascular bed under conditions of controlled pulmonary blood flow and constant left atrial pressure. Under baseline conditions, electrical stimulation of vagal efferent fibers increases lobar arterial pressure. However, when vasoconstrictor tone was increased, a depressor response was unmasked.