RELATIONSHIP BETWEEN MUSCLE MYOSIN ISOFORMS AND CONTRACTILE FEATURES IN RABBIT FAST-TWITCH DENERVATED MUSCLE

The effects of 8-day-old rabbit fast-twitch gastrocnemius denervation on the type of myosin isoforms and on contractile features (maximum ve locity V-max and contraction time (CT) of the muscle were followed bet ween 15 and 60 days postnatal, The myosin isoforms and the V-max and C T values of the denervated gastrocnemius displayed large changes durin g this period, These changes, which led at 2 months postnatal to a mus cle displaying the properties of a slow-twitch muscle did not occur in synchrony:complete conversion to slow-type myosin isoforms occurred o nly at 60 days postnatal, whereas complete conversion to slow-twitch V -max and CT values occurred as soon as 35 days postnatal, The results address a new question concerning the relationship between muscle myos in and contractile features.