SEX DIFFERENCE IN ENZYME ACTIVITIES OF RAT SKELETAL MUSCLES / 体力科学

ABSTRACT

Sex difference in enzyme activities of the skeletal muscle were examined in rats aged 10 and 35 weeks. At 10 and 35 weeks of age, animals were anesthetized with ether and weighed. M, gastrocnemius, m.extensor digitorum longus and m.soleus were removed from both legs under pentobarbital anethesia and weighed. These muscles were used for the determination of myosin ATPase activity, phosphofruktokinase (PFK) activity, succinate dehydrogenase (SDH) activity and non-collagenous protein (NCP) content.<BR>The results were summarized as follows<BR>1) Thirty-five week-old rats had heavier body and muscle weights than 10-weekold rats in both sexes and males had significantly heavier body and muscle weights than females at both 10 and 35 weeks of age.<BR>2) Similar tendency was observed with regard to total NCP content. Furthermore, it was found that total NCP content was positively correrated to muscle weight (r=0.871, r=0.909 and r=0.871 in m. gastrocnemius, m.extensor digitorum longus and m.soleus, respectively) . However, no significant difference in NCP content per wet weight was found between both sexes and between different age groups.<BR>3) Myosin ATPase activity tended to be lower at 35 weeks of age than at 10 weeks of age, the tendency being the most prominent in the gastrocnemius muscle of male rat (p<0.05) . However, no significant sex difference in myosin ATPase activity was observed in three muscle examined in both age groups.<BR>4) Although not statistically significant, mean PFK activity was slightly lower in 35-week-old rats than in 10-week-old rats, and there was no sex difference in PFK activity at both weeks of age.<BR>5) SDH activity was significantly lower in 35-week-old rats than in 10-week-old rats except that there was no significant age difference in the gastrocnemius muscle of males. There was no significant sex difference in SDH activity in both age groups with an exception of the extensor digitorum longus muscle from 35-week-old rats, where males had significantly higher SDH activity than females.