Effect of beta-adrenoreceptor blockade on rat cardiac and skeletal muscle pH

The effect of catecholamines on the intracellular pH of rat cardiac and skeletal muscle during varying extracellular acid-base states was determined. Intracellualr pH (pHi) was calculated from the distribution of [14C]DMO. Acid-base disturbances were produced by placing the animals in an environmental chamber containing 10 or 20% CO2 or by administering HCL or NaHCO3. Two hours later the animals were anesthetized with sodium pentobarbital and blood and tissue samples obtained. In one series of animals, the effects of catecholamines were attenuated by administering the beta-adrenoreceptor antagonist MJ 1999 (Sotalol). In animals breathing 20% CO2, cardiac muscle pH was lower in beta-blocked than unblocked animals (6.69 vs. 6.78). During metabolic acidosis, cardiac muscle pH of beta-blocked animals was lower than that of unblocked animals (6.75 vs. 6.84). The same relationship was observed for skeletal muscle during metabolic acidosis-beta blockade pHi, 6.66; unblocked pHi, 6.77. The pHi of beta-blocked versus unblocked animals was not significantly different under normal acid-base conditions or metabolic alkalosis for cardiac or skeletal muscle. The effective buffer value of both tissue over the normal acidotic range was decreased by the beta-blocking agent. These results indicate that catecholamine release accompanying acidosis attenuates the change in pHI and increases the effective buffer value of cardiac and skeletal muscle.