Actin mRNA levels and myofibrillar growth in leg muscles of the European lobster (Homarus gammarus) in response to passive stretch.

ABSTRACT

An actin cDNA clone from the European lobster, Homarus gamarus, has been generated by RT-PCR and used as a probe to quantify the relative abundance of actin mRNA in lobster leg muscles following imposition of passive stretch by leg flexion. The sarcomere lengths of a population of fibers in the same muscles were measured to provide an indirect marker of myofibrillar growth. Stretch resulted in a 70% increase in actin mRNA levels compared with unstretched controls animals between weeks 1 and 2 after flexion of the legs. Sarcomere lengths increased by 23% immediately after imposition of the stretch. During the same period of observed increase in actin mRNA, the sarcomere lengths returned to their initial values, indicating that longitudinal growth of the myofibrils had occurred. Results are discussed in relation to the role of stretch in crustacean muscle growth during the moult.