Effects of hypoxia on energy state and pH in resting pulmonary and femoralarterial smooth muscles

To determine the effects of hypoxia on energy state and intracellular pH (p H(i)) in resting pulmonary and systemic arterial smooth muscles, we used P- 31 nuclear magnetic resonance spectroscopy and colorimetric and enzymatic a ssays to measure pH(i); intracellular concentrations of ATP, phosphocreatin e, creatine, and P-i; and phosphorylation potential in superfused tissue se gments from porcine proximal intrapulmonary and superficial femoral arterie s. Under baseline conditions (Po-2 467 +/- 12.1 mmHg), energy state and tot al creatine (phosphocreatine + creatine) concentration were lower and pH(i) was higher in pulmonary arteries. During hypoxia (Po-2 23 +/- 2.4 mmHg), e nergy state deteriorated more in femoral arteries than in pulmonary arterie s. pH(i) fell in both tissues but was always more alkaline in pulmonary art eries. Reoxygenation reversed the changes induced by hypoxia. These results suggest that production and/or elimination of ATP and H+ was different in resting pulmonary and systemic arterial smooth muscles under baseline and h ypoxic conditions. Because energy state and pH(i) affect a wide variety of cellular processes, including signal transduction, contractile protein inte raction, and activities of ion pumps and channels, further investigation is indicated to determine whether these differences have functional significa nce.