Embryonic and postnatal development in experimental tryptophan deprived rats. A preliminary study

An ontogenetic and endocrinological study has been designed on developing rats in uterus of mothers tryptophan deprived at day 1 (exp. 1) and day 14.5 (exp. 2) of conception to verify the supposed determining role of the serotoninergic system (SS) in sexual differentiation in mammals. Tryptophan-free feeding has been pursued uninterruptedly in the litter after birth, during lactation and postnatal development. Tryptophan-free pregnant rats were obtained by exclusion of tryptophan sources from chow. In both exp. 1 and exp. 2 the litter showed at birth a significant physical under evolution, that worsened, during post-natal development, to a much more marked dwarfism in exp. 1 pups. At 30 days postnatal age, whereas the female exp. 1 rats showed a right-timed onset of puberty, neither descensus of the testes nor spermatogenesis could be observed in the male rats of the same experiment. Endocrinologically the males showed a significant reduction of plasma FSH levels, but also a slight increase of those of LH. Moreover, a marked hypoandrogenism and a severe hypoprolactinemia characterized the males of this group. Hypoprolactinemia was the major endocrinological finding also in the female litter, which, however, at 30 days p.n. age showed the typical histological patterns of a cycling ovary, i.e. growing secondary follicles with scattered antral spaces, and thus a right-timed pubertal maturation, in spite of the significant lower plasma levels of pituitary gonadotropins and sex steroids. When mothers were tryptophan deprived at 14.5 of pregnancy (exp. 2), the litters showed a less marked dwarfism, persistent, severe hypoprolactinemia as in exp. 1 rats, but a normal right-timed onset of puberty in both male and female rats. Taken together these findings confirm on the one hand the close relationship between SS and PRL. On the other hand, they suggest a major, crucial role of PRL played in the male rat before day 14.5 of intrauterine development, presumably intervening in the synthesis of LH receptors sites by the maturing Leydig cells in the male gonads. Growth hormone concentrations in both sexes dwarf rats were lower than in control rats.