Rapid isolation of total RNA from small mammal and human skeletal muscle

The present study was designed to assess the efficacy and reliability of a method (Anal. Biochem. 162: 156-59, 1987) of total RNA isolation from small muscle samples. The RNA content of skeletal muscles in mouse, rabbit, guinea pig, rat, and human was also investigated. Enough RNA was extractable from muscle samples as small as 25 mg in weight to provide material for the analysis of specific mRNA sequences using RNA blot hybridization with a cDNA probe for a mitochondrially encoded subunit of cytochrome-c oxidase. The RNA was free of detectable levels of protein or DNA. Gel electrophoresis and cDNA probe hybridization indicated that the RNA was relatively undegraded. Significant differences (P less than 0.05) in RNA content were found among fiber types (type I fibers greater than type II fibers) and among the soleus muscles of various species (guinea pig greater than rat = mouse greater than rabbit). Human muscle possessed the lowest RNA content (350 ng/mg) among the species investigated. The results indicate that intact RNA can be rapidly and reliably isolated from small skeletal muscle, including samples typically obtained from human muscle biopsies. This technique should permit the analysis of gene expression in muscle subject to a variety of physiological treatments.