AJP - Endocrinology and Metabolism, Vol 250, Issue 5 558-E563, Copyright © 1986 by American Physiological Society
Rapid effects of insulin on in vitro translational activity of specific mRNA in diabetic rat heart
R. Shanker, W. E. Neeley and W. H. Dillmann
We studied the time course of response of specific cardiac mRNA after
administration of insulin to diabetic rats. The primary aim was to identify
specific cardiac mRNA, which show a rapid response to insulin
administration. Diabetic rats were injected with 2 U of regular insulin
intravenously, and total cardiac RNA was prepared 0.5, 1.5, 3, 5, 12, and
24 h later. RNA was translated in vitro in the presence of [35S]methionine
and the translational products separated by two-dimensional electrophoresis
and quantitated by digital matrix photometry. A rapid change in the
translational activity of five specific mRNA species was observed within
0.5 h after administration of insulin to the diabetic animal. One
translational product exhibits a more delayed response at 1.5 h. The
predominance of three of these products was increased, while that of three
was decreased. Two specific mRNA coding for translation products designated
as spots 97 and 106 show the most significant change, with a dramatic
decrease of 15-fold and 6.5-fold, respectively, within 0.5 h after insulin
administration. The change in levels of these specific mRNA species could
result from effects of insulin at various sites of mRNA synthesis or
degradation. However, the rapidity of the response is compatible with a
direct effect of insulin on gene expression. The very quick response of
these specific mRNA species to insulin could thus serve as a useful model
system to examine the molecular mechanisms of insulin action in the heart.
