Effect of the androgenic status on the phenotype of the plantaris muscle of the rat.

1. The early demonstration of specific androgen binding sites in skeletal muscle suggested that androgen might be involved in the homeostasis of the tissue in adult mammals. 2. Following five weeks of androgen withdrawal, a noticeable increase in the plantaris (PLT) myosin heavy chain cleavage occurs. No other alteration of the contractile proteins pattern was detected. 3. No effect on the template activity of major mRNAs associated with the polysomal fraction was observed in GDX or GDX + TP group compared to control rats. 4. As opposed to the PLT muscle, the template activity of polyribosomes isolated from the androgen sensitive levator ani muscle displays a severe alteration following GDX. 5. Force-frequency analysis of PLT indicated however that the MHC modification was of no functional significance.