Chronic muscle stimulation increases lactate transport in rat skeletal muscle

The aim of this study was to examine the effects of chronic low frequency 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. Chronic stimulation (10 Hz, 50 psec bursts, 24 h/day) commenced 7 days 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 control TA (p < 0.05). Lactate transport (zero-trans) was measured in giant sarcolemmal vesicles obtained from the chronically stimulated TA and the control TA. At each of the concentrations used in these studies a significant increase in lactate transport was observed: 2.8-fold increase 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 transport capacity is markedly increased in response to chronic muscle contraction.