DIFFERENTIAL ISOACTIN GENE-EXPRESSION IN THE SPHINCTERIC AND NONSPHINCTERIC GASTROINTESTINAL SMOOTH MUSCLES OF THE OPOSSUM

The sphincteric smooth muscle tissues of the gastrointestinal tract ha ve been shown to possess mechanical properties distinct from the surro unding nonsphincteric smooth muscle tissues. Little is currently known regarding the molecular basis of this differential smooth muscle deve lopment and function. Actin is an important contractile protein whose expression has been linked to the normal development and function of s mooth muscle tissues. The purpose of this study was to characterize is oactin gene expression in the sphincteric versus nonsphincteric smooth muscle tissues of the gastrointestinal tract. Northern blot analysis was performed on manometrically identified sphincteric and the flankin g nonsphincteric smooth muscle tissues of the adult opossum. Quantitat ive analysis revealed a distinct pattern of isoactin gene expression i n the sphincteric versus nonsphincteric smooth muscle tissues of the g ut. The sphincteric smooth muscle tissues expressed significantly lowe r total quantities of isoactin mRNA than their surrounding nonsphincte ric smooth muscle tissues. It is hypothesized that these differential patterns of isoactin gene expression may play a significant role in es tablishing the myogenic potential of the functionally distinct sphinct eric and nonsphincteric smooth muscle tissues of the gut.