Acta Physiologica 43. (1973)
1. szám - PHYSIOLOGIA - Marton I.-Endrőczi E.: Dose and Time Dependence of Testosterone-Induced Precocious Puberty in Female Rats
Acta Physiologica Academiae Scientiarum Hungaricae, Tomus 43 (1), pp. 49—53 (1973) DOSE AND TIME DEPENDENCE OF TESTOSTERONE-INDUCED PRECOCIOUS PUBERTY IN FEMALE RATS By I. Marton and E. Endrőczi CENTRAL RESEARCH DIVISION, POSTGRADUATE MEDICAL SCHOOL, BUDAPEST (Received September 22, 1972) Recent data indicate that testosterone administration enhances the onset of both vaginal opening and regular cycles in the rat. Studying the effect of testosterone administration on the maturation of the pituitary-gonadal axis, it was found that the increase of ovarian weight after testosterone administration was greatly dependent on the dose and the time of treatment after birth. Testosterone administration in the critical period resulted in a significant increase of ovarian weight but it led to a suppression of pituitary gonadotrophin secretion when given in other prepubertal periods or in inadequate quantity. Concerning the role of sex steroids in maturation of the pituitarygonadal axis, it is known that oestradiol administration results in precocious puberty and an early increase of the pituitary and plasma LH level in prepubertal rats (Ramirez and Sawa'er 1965). This oestrogen-induced precocious puberty Could be prevented by progesterone administration. In connection with the mechanism of oestrogen action, it was suggested that the precocious puberty is due to an earlier maturation of the FSH-RF producing elements in the hypothalamus or to a sensitization to FSH-RF of the pituitary cells by the oestrogen administration (Corbin and Daniels 1969). The first evidence that testosterone administration to immature female rats on the 17th or 19th days of age was effective in advancing the onset of both vaginal opening and regular cycles, was reported by Zarrow et al. (1969), Naqvi et al. (1969) and Naqvi and Johnson (1970). Moreover, they found that pretreatment with progesterone prevented the testosterone-induced precocious puberty. The present investigations were aimed at studying the mechanism of testosterone-induced precocious puberty in the critical period of treatment and the dose-dependence of the phenomenon. Methods A total of 230 immature female R-Amsterdam rats was used in the study. Pregnant females were checked for delivery every morning and the newborns were separated according to their sex. To obtain standard experimental conditions, the size of litters was corrected and each mother cared for 10 13 female offspring. Twenty groups consisting of 10—13 animals each were formed. The litters were kept in individual cages in an air-conditioned room in light and dark, with light from 6.00 a.m. till 6.00 p.m. Food and water were provided ad libitum. Acta Physiologica Academiae Scientiarum Hungaricae 43, 1973 4