In this study we developed an SDS-PAGE protocol which for the first time separates effectively all
myosin heavy chain (MHC)
isoforms expected to be expressed in iliofibularis (IF), pyriformis (PYR), cruralis (CRU) and sartorius (SAR) muscles of the toad Bufo marinus on the basis of previously reported fibre type composition. The main feature of the method is the use of
alanine instead of
glycine both in the separating gel and in the running
buffer. The correlation between the MHC
isoform composition of IF, SAR and PYR muscles determined in this study and the previously reported fibre type composition of IF and SAR muscles in the toad and of PYR muscle in the frog was used to tentatively identify the MHC
isoforms expressed by twitch fibre types 1, 2 and 3 and by tonic fibres. The
alanine-SDS electrophoretic method was employed to examine changes in the MHC composition of IF, PYR, CRU and SAR muscles with the ontogenetic growth of the toad from post-natal life (
body weight < 1 g) to late adulthood (
body weight 200-450 g). The developmental changes in the MHC
isoform composition of the toad IF muscle observed in this study are in very good agreement with those in the fibre type composition of the developing IF muscle reported in the literature.