Intracellular pH measured by 31P-NMR in isolated rat heart during alpha-1-adrenoceptor stimulation

Changes of intracellular pH (pHi) after alpha-1-adrenoceptor stimulation (5 x 10(-5) mol/l phenylephrine in the presence of 10(-6) mol/l timolol) were studied in isolated perfused rat hearts by 31P-NMR spectroscopy in order to use the whole organ without disruption. The contractility was monitored simultaneously in all hearts. Alpha-1-adrenoceptor stimulation gave an alkalinization by 0.02 +/- 0.01 pH-units (mean +/- S.E.M.) after 5 min and by 0.03 +/- 0.01 pH-units (mean +/- S.E.M.) after 15 min. Thus, an intracellular alkalinization after myocardial alpha-1-adrenoceptor stimulation was observed during close to physiological conditions. The elevation of pHi may contribute to maintain the inotropic effect after alpha-1-adrenoceptor stimulation.