AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 1 39-R43, Copyright © 1990 by American Physiological Society
Effect of intestinal bypass on the expression of actin mRNA in ileal smooth muscle
M. Lai, D. B. Thomason and N. W. Weisbrodt
Department of Physiology and Cell Biology, University of Texas Medical School, Houston 77030.
In this study, messenger RNAs (mRNAs) for actin isoforms were assessed in
longitudinal smooth muscle from the ileum of unoperated rats and from rats
that had undergone bypass of the middle 70% of the small intestine. The
plasmid clone pGEM 10C, which contains a DNA insert complementary to the 3'
untranslated region and the region of mRNA that codes for the synthesis of
alpha-smooth muscle actin protein, was used to synthesize two riboprobes.
One probe, complementary to the coding region of the insert, hybridizes to
most, if not all, actin isoform mRNAs. The second probe, complementary to
the 3' untranslated region of the insert, hybridizes only to alpha-smooth
muscle actin mRNA. RNA was isolated from animals 4 to 5 days after
operation, size fractionated by denaturing gel electrophoresis, transferred
to nylon membranes, and exposed to the two 32P-labeled riboprobes. Both
probes hybridized to RNA of about 1.3 kilobases long. Longitudinal muscle
from both groups of animals contained alpha-smooth muscle actin mRNA as
well as mRNA for other actin isoforms. Dot blots of varying amounts of RNA
were hybridized to the riboprobes to determine the proportions of actin
mRNAs. The content and concentration of mRNAs for all actins, and of mRNA
for alpha-smooth muscle actin, were significantly greater in muscle from
the functioning ileum of bypassed animals 4-5 days after the operation.
Thus the operation induces a rapid, specific activation of these
contractile protein genes.
