L-TRYPTOPHAN BINDING TO HEPATIC NUCLEI - AGE AND SPECIES-DIFFERENCES

The present experiments report differences in in vitro nuclear binding affinity for L-tryptophan 1) between livers of young (6 1/2 weeks old ) and older (30 weeks old) NZBWF(1) mice, but not so in similar aged S wiss mice, and also, 2) in livers of hamsters compared to livers of gu inea pigs. In vitro hepatic nuclear specific binding affinity after tu be-feeding L-tryptophan (5-20 mg/100 g body weight) to mice 1 h before killing revealed less in young than in older NZWBF(1) mice, comparabl e to the above in vitro assay studies. In vitro nuclear binding affini ty for L-tryptophan of livers of hamsters was significantly less than that of livers of guinea pigs or Swiss mice. In general, the degree of stimulatory effect on hepatic protein synthesis, as measured by in vi tro [C-14]leucine incorporation into protein using microsomes of anima ls tube-fed L-tryptophan Ih before killing compared to that of animals tube-fed water, correlated with the basal nuclear specific binding af finity to L-tryptophan of the animals (ages and species) used.