EFFECT OF CENTRIFUGATION AT 2G FOR 14 DAYS ON METABOLIC ENZYMES OF THE TIBIALIS ANTERIOR AND SOLEUS MUSCLES

Background: The enzyme composition of different muscle types vary grea tly, leading to different changes of enzyme level caused by exposure t o various stimuli. Methods: Male Wistar rats were centrifuged at 2G in a 12-ft radius centrifuge for 14 d. Tibialis anterior (TA) and soleus muscles from four centrifuge and four control rats were analyzed for three enzymes characteristic of fast twitch muscles (phosphofructokina se, glycerol-3-phosphate dehydrogenase, and pyruvate kinase), and four enzymes characteristic of slow twitch muscles (hexokinase, mitochondr ial thiolase, B-hydroxyacyl CoA dehydrogenase, and citrate synthase). Results: The centrifuged TA muscles lost 15% of their weight; the corr esponding soleus muscles gained 4%. Calculated on the basis of dry wei ght, the fast twitch enzyme activities were reduced 3-15% in the TA mu scles but increased 10-23% in the soleus muscles. The slow twitch enzy mes were reduced 18-30% in TA muscles but were almost unchanged in the soleus muscles. When calculated on the basis oi total muscle weight, all of the enzymes in TA muscles were significantly reduced by centrif ugation. In contrast, in soleus muscles, on the basis of total muscle weight, centrifugation caused an average increase of 22% in the fast t witch enzymes but only marginal changes in the slow twitch enzymes.