Effects of pre and perinatal malnutrition on muscle fibres from fast and slow rat muscles.

Pre and perinatal malnutrition of rats was effected by means of limiting the mothers' food intake by 50% during pregnancy and lactation. Male offspring were sacrificed at 36 weeks of age and the anterior tibialis (ANTIB) and soleus (SOL) muscles were prepared for histochemical demonstration of Type I, IIA and IIB muslce fibre types using myosin ATPase and succinic dehydrogenase activity. Muscle weights and mean muscle fibre area determinations showed greater decreases in ANTIB than SOL, SOL muscle fibre areas being relatively unaffected by the undernutrition regimen. The proportions present of the muscle fibre types differed in ANTIB and to a small extent on SOL. In the former muscle, some decreases in area in certain of the fibres were associated with increases in the percentages present, showing a tendency to maintain the physiological cross-sectional area of the muscle.