INVOLVEMENT OF D-ASPARTIC ACID IN THE SYNTHESIS OF TESTOSTERONE IN RAT TESTES

D-Aspartic acid (D-Asp) is an endogenous amino acid which occurs in ma ny marine and terrestrial animals. In fetal and young rats, this amino acid occurs prevalently in nervous tissue, whereas at sexual maturity it occurs in endocrine glands and above all in pituitary and testes. Here, we have studied if a relationship exists between the presence of D-Asp and the hormonal activity. The following results were obtained: 1) Both D-Asp and testosterone are synthesized in rat testes in two p eriods of the animal's life: before birth, about the 17th day after fe rtilization and, after birth, at sexual maturity. 2) Immunocytochemica l studies have demonstrated that this enantiomer is localized in Leydi g and Sertoli cells. 3) In vivo experiments, consisting of i.p. inject ion of D-Asp to adult male rats, demonstrated that this amino acid acc umulates in pituitary and testis (after 5 h, the accumulation was of 1 2 and 4-fold over basal values, respectively); simultaneously, luteini zing hormone, testosterone and progesterone significantly increased in the blood (1.6-fold, p<0.05; 3.0-fold, p<0.01 and 2.9-fold, p<0.01, r espectively). 4) Finally, in vitro experiments, consisting of the incu bation of D-Asp with isolated testes also demonstrated that this amino acid induces the synthesis of testosterone. These results suggest tha t free D-Asp is involved in the steroidogenesis.