Comparison of muscle fiber types between forelimb and hindlimb in male frogs in breeding season by histochemical activities

Abstract

One of the forelimb flexor muscles, flexor carpi radialis muscle (FCR), in male frogs is used for long-lasting mating posture, so-called amplexus, and its mechanical properties are known to be much different from those in other skeletal muscles, e.g. the hindlimb muscles used for jumping. It was reported previously that both the rates of increase and decrease in contractile force of FCR at the beginning of and after the end of the electrical repetitive stimulation were much slower than those in hindlimb. In the present experiment, we measured histochemical activities of FCR and hindlimb muscles to know the difference in muscle fiber types in frog.We stained FCR muscle and two hindlimb muscles, iliofibularis muscle (IFM) and glutaeus magnus muscle (GMM), in breeding season (Feb.- Mar.) for adenosine triphosphatase (ATPase) with the preincubation in pH 4.9 and 10.1. In addition, these muscles were also stained for succinate dehydrogenase (SDH). With these three histochemical methods, it was demonstrated that FCR in forelimb consisted of various fiber types including slow types, while GMM and IFM in hindlimb consisted of one fast type and of one fast and one slow types respectively. [J Physiol Sci. 2008;58 Suppl:S64]