Endocrinology, Vol 124, 754-761, Copyright © 1989 by Endocrine Society

ARTICLES

Insulin and dexamethasone regulation of a rat hepatoma messenger ribonucleic acid: insulin has a transcriptional and a posttranscriptional effect

JL Messina
Department of Physiology, State University of New York Health Science Center, Syracuse 13210.

Experiments were conducted to investigate the actions of glucocorticoids and insulin on the induction of a specific mRNA (p33- mRNA) expressed in rat H4 hepatoma cells. Previous studies have found a 10-fold increase in this mRNA following 60 min of insulin addition. In the present study, dexamethasone (Dex) induced the cellular concentration of p33-mRNA 10- to 15-fold. This effect was time and dose dependent. The effect of Dex could be accounted for by a 10- to 15-fold increase in p33-mRNA transcription. However, insulin administration resulted in only a 3-fold increase in the transcription of p33-mRNA. The insulin induction of transcription was time and dose dependent and was blocked by the addition of alpha-amanitin. There was no increase in the transcription of a control gene, beta-tubulin, by either insulin or Dex. Neither insulin nor Dex altered the stability of p33-mRNA. Since the cellular concentration of p33-mRNA was induced to a greater extent than was transcription, insulin must be regulating at least one other step in the sequence between RNA synthesis and RNA stability.

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