Studies of gene expression in liver of insulin-like growth factor (IGF)-I, IGF binding protein-3 and growth hormone (GH) receptor/GH binding protein in rats treated neonatally with monosodium glutamate.

We studied the gene expression of the insulin-like growth factor (IGF)-I, IGF binding protein (IGFBP)-3 and growth hormone (GH) receptor (GHR)/GH binding protein (GHBP) in liver of rats treated neonatally with monosodium glutamate (MSG). The MSG-treated rats showed severe growth retardation and obesity compared to saline-injected controls. Serum IGF-I levels in MSG-treated rats were significantly lower than in the controls after 6 weeks of age (p < 0.01). IGF-I gene expression increased with age and was significantly lower in MSG-treated rats than in the controls (p < 0.01). IGFBP-3 gene expression was unaffected by age in both MSG-treated male rats and the controls, but was less in MSG-treated female rats than in their controls between 6 to 8 weeks of age. In our study of GHR/GHBP gene expression, MSG-treated rats of both sexes displayed a distinct 1.5 kbase band encoding GHBP RNA. We speculated that these changes reflect disruption of GH secretion in in vivo experimental models. Thus, MSG-treated rats are useful as in vivo models for study of the effect of GH disruption on developmental gene expression.