Relationship between pH, Po2, and Pco2 on the pulmonary vascular bed of the cat.

VILES, PETER EL, AND JOHN T. SHEPHERD. Relationship between pH, PO 2, and PCO~ on the pulmonary vascular bed of the cat. Am. J. Physiol. 215(5) : 1170-l 176. 1968.-In order to study the relationships between pH, Paz, and Pcoz on pulmonary vessels, isolated cat lungs were perfused at constant flow with autologous blood at 37 C and ventilated with 20, 10, 5, and 2.5y0 oxygen. PCO~ was either zero or 60 mm Hg. Airway and left atria1 pressures were constant. Lactic acid (0.3 N) or sodium bicarbonate (0.9 M) was infused to alter pH. In six lung preparations with Pcoz zero and pH 7.6, pressor responses to hypoxia were attenuated or absent. Lowering the pII to 7.0, with oxygen tension 120 mm Hg, caused the mean pulmonary artery pressure (Ppa) to increase from 17 to 25 mm Hg and augmented the pressor responses to hypoxia. In six lung preparations with Pcoa at 60 mm Hg and pH about 7.6, Ppa increased from 14 to 26 mm Hg with severe hypoxia (Paz = 20 mm Hg); lowering the pH to about 7.0, with oxygen tension 120 mm Hg, caused Ppa to increase from 14 to I6 mm Hg, and near maximal increases in Ppa (11 mm Hg) occurred with a POT of 40 mm Hg. In intact cats, hypoxic responses were absent at pH above 7.5. The data indicate a possible relationship between intracellular pH and hypoxic pulmonary vasoconstriction’