Research Information System
FASEB Journal, vol.12, no.5, 1998 (SCI-Expanded)
A new cardiac catheterization technique was used to investigate pulmonary pressure-blood flow relationships in intact spontaneously breathing rats (ISBR) under physiologic conditions with constant left atrial pressure and controlled blood flow within the normal range. The pressure-flow curves in vivo were curvilinear with pulmonary arterial pressure increasing more rapidly at low pulmonary blood flows of 4-8 ml/min, and less rapidly at higher flow rates. Pressure-flow curves were reproducible, and were not altered by 1-1.5 hr period of arrested perfusion, cyclooxygenase blockade, or perfusion with aortic or mixed venous blood. In the intact animal, NG-nitro L-arginine methyl-ester (L-NAME) increased pulmonary arterial pressure at all but the lowest flow rates with a slight effect on the curvilinear pressure-flow relationship. L-NAME attenuated pulmonary vasodilator responses to acetylcholine, bradykinin, adrenomedullin-(13-52) and enhanced the pulmonary vasodilator response to nitroglycerin. The present data suggest that actively-induced pulmonary hypertension is under greater control by endothelium-derived-relaxing factor (EDRF). Results in ISBR demonstrate the pulmonary vasodilator response to adrenomedullin-(13-52) is not mediated by calcitonin gene-related peptide (CGRP) receptors which are not coupled to the release of EDRF and that EDRF may play a role in the regulation of vascular tone at high flow rates. These results indicate that this new technique may provide a useful model for the study of the pulmonary circulation in the intact-chest rat.