Determination of the relative abundance of skeletal muscle alpha actin mRNA in muscle of livestock species.

Three market-weight animals of meat-producing livestock species were slaughtered to obtain porcine (barrows), bovine (steers), ovine (wethers), and avian (cockerels) tissue samples. The four tissues of interest were skeletal muscle, heart, smooth muscle (stomach or gizzard), and liver. Total RNA was isolated from each tissue and then hybridized to a human skeletal (sk)-alpha-actin [32P]cDNA probe using both dot blot and Northern blot hybridization. No hybridization was observed with RNA from liver or smooth muscle from any of the species, suggesting little or no hybridization to nonmuscle and smooth muscle beta- and gamma-actin isoforms. The human sk-alpha-actin probe hybridized to RNA from skeletal muscle of pigs, cattle, sheep, and chickens, although relative hybridization was 75% less with chicken RNA. The hybridization was limited specifically to a band at 1.6 kb (kilobases), the known length of sk-alpha-actin mRNA. Hybridization was observed with RNA from pig heart (1.6 kb) and the relative abundance was consistently 7 to 10% of that observed with porcine skeletal muscle, even as stringency conditions were increased. These results indicate that the human sk-alpha-actin probe can be used to determine alpha-actin mRNA expression in skeletal muscle for pigs, cattle, and sheep.