ELECTROPHORETIC ANALYSIS OF MYOSIN HEAVY-CHAIN ISOFORM PATTERNS IN EXTRAOCULAR-MUSCLES OF THE RAT

Six oculorotatory muscles and the levator palpebrae muscle of the rat were analysed by SDS-PAGE for their myosin heavy chain (MHC) isoform p atterns. Oculorotatory muscles display a marked predominance of fast M HC isoforms. They contain, in addition to the slow (MHCI) and fast (MH CIIb, MHCIId, MHCIIa) skeletal MHCs, the neonatal MHC(neo) and the ext raocular MHC(eom). The levator palpebrae, generally assumed to be a me mber of the extraocular muscle group because of its innervation by the ocolumotor nerve, does not contain MHC(neo) and MHC(eom). It resemble s a fast-twitch skeletal muscle with a predominance of MHCIId.