Nutrition and somatomedin XXII. Molecular regulation of insulin-like growth factor-1 during fasting and refeeding in rats

The liver is thought to be the locus of nutritional/ hormonal regulation of circulating insulin-like growth factor-I (IGF-I). To probe the basis of nutritional regulation, we examined changes in serum IGF-I, hepatic content of extractable IGF-I immunoreactivity (a high Mr putative precursor) and hepatic IGF-I mRNA during fasting and refeeding in rats. Preliminary studies revealed that the hepatic level of IGF-I mRNA was consistently reduced only after food was withheld for 3 days, so the effects of refeeding were subsequently examined in such animals. After 3 days of fasting, animals lost 30 % of their initial weight; weight regain was apparen