Actin and creatine kinase mRNAs in rat levator ani and vastus muscles as a function of androgen status

Area of Science:

• Molecular Biology
• Muscle Physiology
• Endocrinology

Background:

• Androgens play a crucial role in regulating gene expression and protein synthesis in various tissues.
• Skeletal muscles exhibit varying sensitivities to hormonal influences, impacting their plasticity and function.
• Orchiectomy (GDX) provides a model to study the effects of androgen deprivation on muscle tissue.

Purpose of the Study:

• To investigate the differential effects of androgen deprivation on mRNA expression in two distinct rat fast-twitch skeletal muscles.
• To compare the plasticity of the androgen-sensitive levator ani (LA) muscle with the androgen-insensitive superficial vastus lateralis (SVL) muscle following orchiectomy.

Main Methods:

• Quantitative analysis of actin and creatine kinase (CK) mRNA expression in LA and SVL muscles at various time points post-orchiectomy (GDX).
• In vitro translation assays to assess the functional activity of isolated mRNAs.
• Hormone replacement therapy using testosterone propionate (TP) to evaluate recovery of gene expression.

Main Results:

• Actin mRNA expression in the LA muscle decreased by 85% 10 days after GDX, with recovery after TP administration.
• SVL muscle actin mRNA expression remained largely unchanged up to 20 days post-GDX.
• Creatine kinase (CK) mRNA levels in LA showed transient increases and subsequent decreases post-GDX, while CK activity and in vitro translation remained elevated.
• CK mRNA expression in SVL muscle was unaffected by GDX.

Conclusions:

• The levator ani (LA) muscle demonstrates significant plasticity in response to androgen deprivation, with marked downregulation of actin mRNA.
• The superficial vastus lateralis (SVL) muscle exhibits considerably lower sensitivity to androgen withdrawal compared to the LA muscle.
• Differential gene expression patterns underscore the distinct roles of androgens in regulating protein synthesis in various skeletal muscle types.