Growth hormone induction of insulin-like growth factor I messenger RNA in primary cultures of rat liver cells.

Primary liver cells from adult rats were used to study the hormonal regulation of mRNA coding for insulin-like growth factor I (IGF-I). IGF-I mRNA could be detected at a low concentration in liver cells prepared from hypophysectomized rats and cultivated for 3 days. When these cells were exposed to GH on the second day, a dose-dependent increase in IGF-I mRNA was observed. The continuous presence of serum was not a prerequisite for this response, since GH also induced IGF-I mRNA in a defined hormone-supplemented medium. It is concluded that GH can induced IGF-I mRNA in the liver by a direct mechanism.