Effects of adrenalectomy or RU-486 on rat muscle fibers during hindlimb suspension.
The purpose of this study was to investigate the effects of a glucocorticoid antagonist, RU-486, and of adrenalectomy (ADX) on rat skeletal muscle structural properties after 3, 7, and 14 days of hindlimb suspension (H). After H, a significant loss in muscle weight was observed as early as 3 days in soleus (SOL; -10%) and adductor longus (AL; -14%) muscles. In SOL, after only 7 days, a reduction (-14%) in type I fiber percent distribution occurred, accompanied by an increase (+129%) in intermediate type I fibers. Fiber type changes increased depending on the duration of H. In AL muscle, no change occurred after H in the fiber type composition despite a similar degree of muscle atrophy. Treatment with RU-486 or ADX significantly reduced the loss of SOL weight observed after 14 days (-42 and -44%, respectively, vs. -50% for H rats), delayed the SOL atrophy (from 3 to 7 days), and normalized the shift in fiber type distribution induced by H. In SOL, administration of RU-486 (but not ADX) partly prevented the reduction in size induced by H of all the fibers. In AL, neither treatment affected the extent of muscle atrophy, even though the reduction in type IIa fiber size was prevented by RU-486 but not by ADX after 14 days of suspension. ADX or RU-486 administration did not prevent the extensor digitorum longus weight loss observed after 14 days of suspension but allowed a recovery of its normal fiber type composition.(ABSTRACT TRUNCATED AT 250 WORDS)
Aboudrar
S
S
Unité de Recherche Associée 1341, Centre National de la Recherche Scientifique, Laboratoire de Physiologie, Faculté de Médecine de Lyon Grange Blanche, France.
Sempore
B
B
Koubi
H
H
Dechaud
H
H
Desplanches
D
D
D000315:Adrenalectomy; D000818:Animals; D001284:Atrophy / Q000503:physiopathology; D002454:Cell Differentiation / Q000187:drug effects; D003345:Corticosterone / Q000097:blood; D005260:Female; D006651:Histocytochemistry; D007328:Insulin / Q000494:pharmacology; D015735:Mifepristone / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D009929:Organ Size / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013963:Thyroid Hormones / Q000494:pharmacology; D014893:Weightlessness / Q000009:adverse effects*
D007328:Insulin; D013963:Thyroid Hormones; D015735:Mifepristone; D003345:Corticosterone