Changes in myosin and actin filaments in fast skeletal muscle after denervation and self-reinnervation.
1. Myosin and actin filaments of the contractile apparatus of the denervated and self-reinnervated rat leg fast muscle were examined in ultrastructure. In parallel, the total contents of actin and of myosin heavy chains (MHC) were investigated. The results were compared with the corresponding ones in the slow muscle. 2. In the denervated-atrophying fast muscle the myosin filaments disappeared before the actin filaments. However, in contrast to the slow muscle, the local disproportion between the filaments was soon compensated, and their hexagonal arrangement was maintained for about one month after denervation. The contents of MHC and actin decreased, but their ratio remained similar to that in the controls. 3. In the later stage of atrophy the proportion of myosin to actin filaments and the ratio of the corresponding proteins decreased, and the hexagonal arrangement of filaments was disturbed. The denervated fast and slow muscles became similar (in the latter, such changes occurred during the initial weeks after denervation). 4. In the fast muscle recovering after reinnervation (on the third week after denervation) the numbers of myosin and actin filaments, and the contents of the corresponding proteins increased in parallel and the hexagonal arrangement of filaments was maintained (differently than those observed in the slow muscle).
Jakubiec-Puka
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Nencki Institute of Experimental Biology, Warsaw, Poland.
D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D005260:Female; D008854:Microscopy, Electron; D009121:Muscle Denervation; D009132:Muscles / Q000294:innervation* / Q000378:metabolism* / Q000648:ultrastructure; D009133:Muscular Atrophy / Q000378:metabolism / Q000473:pathology; D009218:Myosins / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D000199:Actins; D009218:Myosins