[The dose dependence of 15N-incorporation in organ proteins of newborn rats after pulse labeling with different tracers].

A short-chain 15N-peptide mixture characterized by an average chain length of 2.3 was obtained when 15N-labeled yeast protein has hydrolyzed enzymatically by thermitase from Thermoactinomyces vulgaris. Fifteen newborn Wistar-rats were given a single pulse of [15N]glycine. [15N]H4Cl and [15N]yeast protein-thermitasehydrolysate (YPTH) in a dosage of 50 mg 15N excess kg-1 by gastric tube. In comparison with [15N]glycine the 15N-incorporation rates of brain, muscle and liver were approximately 150% higher after [15N]YPTH-application. Uniform labeling, high 15N-enrichment, almost complete absorption, avoidance of imbalances and the low price make this tracer substance superior to other tracers conventionally used for organ labeling.