Formation and Excretion of Taurine in X-irradiated Rats

Summary

Urinary excretion profiles of taurine have been estimated in male Wistar rats exposed to doses of x-rays ranging from 100–1000 R. Maximum levels were observed in urine collected 24 hours after irradiation. Urinary taurine returned to normal values within 48 hours only in rats which had received sublethal doses (100–400 R). The high taurine levels persisted even after 72 hours in rats receiving more than LD₅₀, i.e. 600–1000 R. The dose–response relationship obtained indicates a sort of a threshold dose beyond which the recovery mechanisms apparently do not operate.

Urinary excess of taurine could be ascribed to enhanced liver cysteic acid decarboxylase activity. The increase in enzyme activity corresponds to the maximum appearance of taurine in the urine. Cysteine sulphinic acid decarboxylase did not show any variation.

Formation of taurine in vivo was also followed up after intraperitoneal injection of cysteine-3-¹⁴C. There was enhanced recovery of radioactivity of the injected amino acid in blood and urine of x-irradiated animals, indicating increased synthesis of taurine. Hypertaurinuria could be prevented by prior treatment with desoxypyridoxine.