THE EFFECT OF LOWERED PH ON THE CA2 -ACTIVATED CONTRACTILE CHARACTERISTICS OF SKELETAL-MUSCLE FIBERS FROM ENDURANCE-TRAINED RATS

Abstract

The effects of acidosis on the contractile characteristics of single, skinned fast- and slow-twitch skeletal muscle fibres were investigated in both sedentary and endurance-trained rats. The trained rats were subjected to a long-term 16 week programme of high-intensity endurance swimming, and carried a load (corresponding to 2% of body mass) during all 2 h sessions. Intracellular acidification, which has been shown in many studies to contribute to the process of muscular fatigue, was mimicked by lowering the pH (from pH 7.1 to 6.6) of the Ca(2+)-buffered solutions bathing isolated, skinned (demembranated) muscle fibres. Activation at both levels of pH enabled comparisons between muscle contr..