The effects of acute ethanol administration (75 mmol/kg body weight) to male Wistar rats (either ad libitum fed or nutritionally restricted) on fractional rates of protein synthesis in the jejunum was assessed together with the changes in IGF-1 and IGF binding protein concentrations. Acute administration of ethanol resulted in significant decreases in fractional rates of protein synthesis in the whole jejunum and jejunal seromuscular layers of both the ad libitum fed and nutritionally restricted animals. The synthesis rate per unit RNA (k(RNA), mg protein/day/mg RNA) in whole jejunum was reduced by 29% and 24% in the nutritionally restricted and ad libitum fed animals, respectively. Mean IGF-1 levels were lower in the nutritionally restricted group (871 +/- 36.9 microg/l) than the ad libitum animals (960 +/- 27.3 microg/l) although this did not reach significance. In contrast, administration of alcohol to both groups markedly reduced circulating IGF-1 levels (ad libitum: 518 +/- 19.8 microg/l, nutritionally restricted: 417 +/- 33.7 microg/l). Furthermore, ethanol treatment resulted in a three-fold increase in the intensity of a 30 kDa IGF binding protein (IGFBP) in the ad libitum fed animals and a fourfold increase in both 30 and 32 kDa IGFBP bands in the nutritionally restricted group as visualized by Western ligand blotting. Decreases in levels of IGF-1 allied with increased circulating small molecular weight IGFBPs may contribute to the reduction in fractional rates of protein synthesis in the gastrointestinal tract of ethanol-treated rats.