Experimental corticosteroid myopathy: effect on myofibrillar ATPase activity and protein degradation.
Corticosteroid myopathy was studied in young, mature New Zealand white rabbits given daily injections of betamethasone (0.3 mg/kg body weight/day) for two weeks. Control rabbits were pair-fed and received saline injections. Bethamethasone treatment caused significant wasting of type 2 gluteus medius and psoas muscles but did not cause any atrophy of type 1 soleus and gluteus minimus muscles. The Mg2+- and Ca2+-activated myofibrillar ATPase activities of the corticosteroid-treated rabbits did not differ from controls despite a 30% reduction in muscle wet weight and pronounced reduction in cross-sectional area of fibers. SDS-polyacrylamide gel electrophoresis profiles of myofibrillar proteins did not differ quantitatively or qualitatively between experimental and control rabbits. Studies of net muscle protein degradation (using 3H-leucine) in betamethasone-treated and control rabbits indicate that both type 1 and type 2 muscle fiber proteins are degraded several times faster in the corticosteroid-treated group. This suggests that a compensatory mechanism exists for those type 1 and mixed fiber type muscles which have increased degradation but do not undergo wasting.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D001623:Betamethasone / Q000494:pharmacology*; D001835:Body Weight / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009124:Muscle Proteins / Q000378:metabolism*; D009132:Muscles / Q000187:drug effects / Q000201:enzymology*; D009135:Muscular Diseases / Q000139:chemically induced* / Q000378:metabolism; D009210:Myofibrils / Q000187:drug effects / Q000201:enzymology; D009929:Organ Size / Q000187:drug effects; D011817:Rabbits
D009124:Muscle Proteins; D001623:Betamethasone; D000251:Adenosine Triphosphatases