CHRONIC MUSCLE STIMULATION INCREASES LACTATE TRANSPORT IN RAT SKELETAL-MUSCLE

The aim of this study was to examine the effects of chronic low freque ncy stimulation on the lactate transport across the plasma membrane of the tibialis anterior (TA) muscle of the rat. Stimulating electrodes were implanted on either side of the peroneal nerve in one hindlimb. C hronic stimulation (10 Hz, 50 mu sec bursts, 24 h/day) commenced 7 day s after surgery, and were continued for 7 days, Animals were then left for 24 h, and thereafter muscles were obtained. Cytochrome C-oxidase activity was increased 1.9-fold in the stimulated TA compared to the c ontrol TA (p < 0.05). Lactate transport (zero-trans) was measured in g iant sarcolemmal vesicles obtained from the chronically stimulated TA and the control TA. At each of the concentrations used in these studie s a significant increase in lactate transport was observed: 2.8-fold i ncrease at 1 mM lactate p < 0.05); 2-fold increases at both 30 mM and 50 mM lactate p < 0.05). These studies have shown that lactate transpo rt capacity is markedly increased in response to chronic muscle contra ction.