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 velocity V-max and contraction time (CT) of the muscle were followed between 15 and 60 days postnatal, The myosin isoforms and the V-max and CT values of the denervated gastrocnemius displayed large changes during this period, These changes, which led at 2 months postnatal to a muscle displaying the properties of a slow-twitch muscle did not occur in synchrony:complete conversion to slow-type myosin isoforms occurred only 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 myosin and contractile features.