Changes in intracellular pH regulation of skeletal muscle of rats with aortic stenosis.

Intracellular pH (pHi) of triceps, trapezius, quadriceps and gastrocnemius muscle tissue was determined in rats with myocardial hypertrophy due to experimental aortic stenosis (AS) and in sham operated rats (SO). During normocapnia, no significant difference in pHi between AS and So animals was observed in any of the muscle species investigated. In hypercapnia (FICO2 0.06, 0.075 or 0.100) pHi of AS was significantly higher than pHi of SO in all muscles, despite no difference in pHe, PaCO2 or [HCO3]a between AS and SO. Therefore, AS appears to be associated with an improvement of pHi regulation in skeletal muscle. In this respect, skeletal muscle behaves as hypertrophic cardiac muscle, which also shows an increased ability to regulate pHi in AS. These results suggest that the changes in pHi regulation of hypertrophic myocardium are not due to the hypertrophic process per se, but to a general phenomenon secondary to AS.