Accumulation of Acid Soluble Peptides in Rat Liver in vivo after Injection of Bestatin

Intraperitoneal injection of bestatin, a microbial aminopeptidase inhibitor, resulted in accumulation of acid soluble peptide-form amino acids in liver of fasting rats. This aminopeptidase inhibitor caused a slight increase in the rate of urinary excretion of acid soluble peptide-form amino acids. However, the excretion rates of only two amino acids of the acid soluble peptide-form were statistically higher in the bestatin injected rats than in the control rats. Leupeptin, another microbial protease inhibitor, also resulted in peptide accumulation in liver of fasting rats. However, it was less effective than bestatin. Leupeptin did not show any effect on the rate of urinary excretion of acid soluble peptides in rats under the present experimental conditions. These results suggest that bestatin sensitive protease (s) may participate in the process of protein degradation in the liver (and presumably in other tissues also), especially in the steps of the degradation of oligopeptides into amino acids.