Effect of pH and lactate on glucose uptake by red and white skeletal muscle in vitro

The diaphragm muscle (the red muscle) and m. obliquus externus abdominis (the white muscle) were incubated in phosphate buffer at pH 7.4 and 6.8 in the presence of different concentrations of sodium lactate (0, 5, 10 and 30 mM). None of the used lactate concentrations changed significantly glucose uptake by the both muscles at pH 7.4. At pH 6.8 lactate in a concentration of 30 mM decreased significantly glucose uptake by the white muscle. At pH 7.4 glucose uptake by the white muscle was significantly lower than that by the red one in the presence of 10 and 30 mM of sodium lactate while at pH 6.8 in the absence of lactate and in the presence of 5 and 30 mM of lactate. Acidosis affected in smaller degree glucose uptake by the red muscle than by the white one. It may be supposed that the impairement of glucose uptake by acidosis and lactic acid in strenously working skeletal muscles can limit the amount of energy sources available for the muscles. Subsequently, it may be one of the factors limiting the ability of the muscles to continue the exhausting exercise.