Comparison of the Effects of Prostaglandins F 1α,F 2α,F 1β,and F 2β on the Canine Pulmonary Vascular Bed 1

The prostaglandins are a group of closely related naturally occurring acidic lipids which possess diverse biological activity (1-3). The effects of the prostaglandins on the peripheral circulation have been studied extensively and in most peripheral vascular beds E series prostaglandins are potent vasodilators whereas F type prostaglandins are weak vasoconstrictor agents (3-8). In the canine pulmonary vascular bed PGE₁ is a moderately active vasodilator whereas PGE₂ is a weak vasoconstrictor agent (9-11). In contrast PGF_2α is one of the most potent pressor substances known in the canine pulmonary vascular bed, and infusion rates which establish concentrations of less than 9 ng/ml in lobar arterial blood increase pulmonary vascular resistance by more than 100% (9, 10). Although the effects of PGF_2α on the pulmonary vascular bed have been documented, nothing is known about the direct effects of PGF_1α, PGF_1β, and PGF_2β on the pulmonary circulation. The purpose of the present investigation was to compare the effects of PGF_1α, PGF_1β, PGF_2α, and PGF_2β on the canine pulmonary vascular bed under conditions of controlled blood flow in the intact spontaneously breathing dog.

Methods. Thirty-five mongrel dogs (16-25 kg) were anesthetized with pentobarbital sodium (30 mg/kg iv) and were strapped in the supine position to a Philips fluoroscopic table. The trachea was intubated with a cuffed endotracheal tube and the animals spontaneously breathed room air. A specially designed 20F double-lumen balloon catheter was positioned in the artery of the left lower lung lobe from the external jugular vein under fluoroscopic guidance (Philips 6-in. intensifier). A Teflon catheter with its tip positioned 2 cm distal to the balloon catheter was used to measure perfusion pressure in the lobar artery. Catheters with side holes near the tip were passed into the main pulmonary artery and the aorta and into a small pulmonary lobar vein and the left atrium transseptally.