SEASONAL-VARIATION IN THE PHENOTYPE OF ADULT FERRET (MUSTELA-PUTORIUS-FURO) CREMASTER MUSCLE

Using immunocytochemistry, electrophoresis and immunoblotting, we stud ied the expression of fast and slow myosin heavy chain isoforms in adu lt ferret muscles during quiescent and breeding periods. Adult cremast er muscle expressed slow and fast myosin heavy chain in relatively sim ilar amounts during the quiescent period. During the breeding period, the expression of slow myosin heavy chain I, significantly decreased, and fast myosin heavy chain II, was predominant. No alteration of the MHC pattern in EDL and soleus muscles was detected between the quiesce nt and breeding periods. The possible involvement of androgens and mec hanical factors in the regulation of myosin heavy chain expression in adult cremaster muscle is discussed.