EFFECTS OF CARNITINE ON PRECONDITIONED LATISSIMUS-DORSI MUSCLE AT DIFFERENT BURST FREQUENCIES

Exercise and electrical stimulation may result in a decrease in carnit ine levels associated with preconditioned latissimus dorsi muscles. Th erefore, the effects of exogenous carnitine were studied in a model of latissimus dorsi muscle contraction. Twelve dogs were studied. Under anesthesia, the latissimus dorsi was placed around an implantable mock circulation system. The muscle was made fatigue-resistant with the ai d of chronic low-frequency electrical stimulation. Six animals receive d carnitine 0.15 mmol/kg; the other six served as control. The muscles were stimulated with 20, 43, and 85 Hz pulse training. During the 90- minute stimulation period, the pressure that developed in the mock cir culation was measured at 15 minute intervals. The changes in ATP and l actate levels were measured every 30 minutes. Stimulations at 20 and 4 3 Hz did not result in any change in pressure or metabolic data over t he course of 90 minutes of stimulation. When the 85 Hz burst was appli ed, ATP levels decreased, while lactate levels increased, with an asso ciated drop in pressure in the control group. ATP and lactate levels w ere, respectively, 13.8 +/- 1.4 mu mol/g and 15.0 +/- 4.0 mu mol/g in the carnitine group and 10.3 +/- 1.1 mu mol/g and 23.0 +/- 3.0, mu mol /g in the control group at the end of 90 minutes (p < 0.05). The press ure at the same time interval was 74 +/- 4 mmHg in the control group, and 85 +/- 3 mmHg in the carnitine group (p < 0.05). In this study, we demonstrated that carnitine administration enhances muscle performanc e in terms of metabolic and pressure changes during high-frequency ele ctrical stimulation at 85 Hz.