In vivo measurements of the tissue accumulation of alpha-amino[1-14C] isobutyrate ([1-14C] AIB) clearly indicate that the hepatic accumulation of the amino acid is not increased in the fed late pregnant rat. Starvation induced an increases in the hepatic AIB accumulation both in virgin and late pregnant animals, thus suggesting that AIB accumulation by the liver is dependent on food intake. The results suggest that amino acids are similarly directed to the conceptus and the liver during late gestation in the rat.