Abstract
Carnosine and anserine are histidine-containing dipeptides that are present in the brain, heart, skin, liver, kidney and skeletal muscle. Various physiological actions have been ascribed to carnosine in skeletal muscle including pH buffering, acting as an antioxidant, the regulation of Ca2+sensitivity and excitation-contraction (E-C) coupling. PURPOSE: The hypothesis tested in this study was that dietary chicken breast extract (CBEX), a rich source of carnosine and anserine, would attenuate deteriorations in sarcoplasmic reticulum (SR) function that occur with high-intensity exercise. METHODS: The CBEX was prepared from the pectoralis major muscles of chicken and mixed with 9 volumes of standard rat chow. Following 5 weeks of dietary CBEX, SR Ca2+-uptake rate, Ca2+-release rate and Ca2+-stimutated ATPase activity were examined in homogenates of the superficial portion of vastus lateralis muscles from rats subjected to high-intensity treadmill running for 2.5 min. RESULTS: Dietary CBEX caused an approximately 15 and 45% increased (P < 0.01) in the muscle carnosine and anserine concentrations, respectively, but no changes in the SR Ca2+-handling ability, i.e., Ca2+-uptake and release rates, in resting muscle. Our data confirm that high-intensity exercise evokes depressions in SR Ca2+-handling. In spite of the same run time, SR Ca2+-handling was reduced to a lesser degree in muscle from CBEX-containing chow-fed rats, compared to standard chow-fed rat. Alterations in SR Ca2+-ATPase activity were not paralleled by those in Ca2+-uptake. Dietary CBEX elicited a 12.4% reduction (P < 0.05) in the catalytic activity of resting muscle. After exercise, the activity was depressed to similar extents between CBEX-containing chowand standard chow-fed rats. CONCLUSIONS: These results implicate the modified SR Ca2+-handling ability as one contributor to inhibition of the fatigue development resulting from carnosine and anserine.
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