A histochemical and morphological study of skeletal muscle from obese hyperglycaemic ob/ob mice.

The histochemical and morphological characteristics of muscles from lean and obese hyperglycaemic ob/ob mice were compared to determine the nature of the low skeletal muscle mass of the latter. Gastrocnemius and biceps brachii muscles from obese ob/ob mice were significantly lighter than those from lean mice, whereas the weights of soleus muscles were not significantly different. The small mass of the biceps brachii muscle resulted from a decrease in diameter of the large glycolytic fast white and fast intermediate fibres and a reduction in the proportion of fast white fibres. The size and frequency of the more oxidative fast red fibres was not different. The histochemical appearance of all fibre types studied from muscles in obese mice was identical to equivalent fibres in lean mice. The fat content of muscles from obese mice was three times greater than in lean mice whereas muscle DNA concentration was similar.