Abstract

To investigate whether or not retardation of body weight (BW) increase by reduced food intake could change enzyme activities in the soleus and extensor digitorum longus (EDL) muscles during growth, rats were divided into 3 groups. Group 1 included rats aged 5, 7, 9, 11 wk fed ad libitum. Group 2 included rats aged 5, 7, 9, 11 wk fed a restricted diet. These animals weighed as much as the 5-wk-old rats in group 1. Group 3 included 4 subgroups of 11-wk-old rats. Their BWs were adjusted to the weights of rats 5, 7, 9 and 11 wk old in group 1 by food restriction. Succinate dehydrogenase (SDH) activity in the soleus increased significantly with growth. Though a similar change was not observed with age in group 2, SDH activity in the soleus in group 3 was enhanced with increasing BW. Phosphofructokinase (PFK) activity in the soleus decreased with growth in groups 1 and 2, but this change was not statistically significant. In group 3, PFK activity in the soleus did not fluctuate with increasing BW. In groups 1 and 2 there was a significant correlation between PFK activity and percentage area of type I fibers in the soleus, but no significant relationship between them was evident in group 3. PFK activity in the EDL increased significantly with growth in groups 1 and 2, but did not change with increasing BW in group 3. It is suggested that the increase of SDH activity in the soleus between the ages of 5 and 11 weeks is influenced primarily by changes in body weight but changes in PFK are not modified by this factor. Verf.-Referat