RELATIONSHIPS BETWEEN MUSCLE CARNITINE, AGE AND OXIDATIVE STATUS

Muscle carnitine levels were examined in 31 younger [mean (SD), 27 (5) years] and 27 older [49 (8) years] men. Needle biopsies were obtained from the lateral gastrocnemius or vastus lateralis muscles and assaye d for free and total carnitine concentrations via a 5,5'-Dithiobis-(2- nitrobenzoic acid) DTNB-linked spectrophotometric procedure. A subgrou p of subjects (n = 28) were assessed for citrate synthase (CS) and suc cinate dehydrogenase (SDH) activity, and type I muscle fiber compositi on (% type I fibers). An additional sub-group of nine subjects was ass essed for free and total serum carnitine levels. No mean (SEM) differe nces in free [21.6 (0.7) vs 20.3 (0.9) mu mol . g dry weight(-1)] and total [26.4 (0.6) vs 26.1 (0.9) mu mol . g dry weight(-1)) muscle carn itine levels were found between the younger and older subjects, respec tively. Correlational data. revealed no significant relationships betw een total muscle carnitine and CS (r = - 0.36), SDH (r = - 0.26), or % type I fibers (r = - 0.16). In addition. there was a low non-signific ant relationship between serum and muscle total carnitine concentratio ns (r = - 0.44). These findings suggest that muscle carnitine levels a re similar between younger and older males, and there does not appear to be any relationship between muscle carnitine and markers of muscle oxidative potential (i.e., oxidative enzymes, % type I fiber). Since s erum carnitine is often used as an indicator of body carnitine status, it is noteworthy that we found a low negative relationship between bl ood and muscle carnitine concentrations.