Total follicular populations and peripheral plasma concentrations of LH, FSH, prolactin, oestradiol-17 beta and progesterone during the preceding cycle were studied in two breeds of sheep (Romanov and Ile-de-France) which differed widely in their ovulation rates (3.2 and 1.5 respectively). No LH parameters could be correlated with the follicular details measured. The second peak of FSH occurring 20-30 h after the preovulatory surge of LH was significantly larger in the Romanov ewes and the area under this peak was correlated (P less than 0.01) with the number of antral follicles present in the ovary 17 days later. This suggests that formation of the antrum during the follicular growth phase is under the control of FSH. The discharge of prolactin preceding the LH peak, although not significantly different between breeds, was correlated with several of the follicular classes measured, including the number of preantral follicles. The peak value of oestradiol-17 beta measured before the LH peak was significantly higher (P less than 0.05) in the Romanov ewes and was correlated with the number of the largest follicles present. There was no significant difference between breeds in the concentration of oestradiol at the onset of oestrus. The progesterone concentration during the luteal phase was highly correlated with the number of preovulatory follicles.
Plasma hormone concentrations before and during luteolysis (induced by injection of a prostaglandin analogue on Day 10 or 11 of the cycle), during the period of preovulatory follicle growth and ovulation were examined in sheep with known differences in ovulation rate (Romanov, Préalpes, Romanov x Préalpes cross, Ile de France). The number of CL at the time of treatment and the ovulation rate in the ensuing cycle were established by endoscopy. Plasma concentrations of FSH, LH, progesterone and total oestrogen were measured by radioimmunoassays in the 3 days before PG injection, then hourly for the 24 h after PG injection and 2-hourly for a further period up to about 100 h after PG injection. The onset and duration of oestrus were also recorded. Although breed differences were observed for many of the features studied, only the intervals between oestrus and the LH peak and between PG injection and the LH peak were significantly correlated with ovulation rate.
Abstract.
Plasma testosterone, LH and FSH levels were determined and correlated with reproductive organs growth, testicular differentiation, fighting and mounting behaviour in maturing rabbit.
An infantile phase of development extends from birth to 40 days, characterized by low testosterone and FSH levels, decreasing LH levels (until 20 days) and by a slow growth of testis and seminal vesicle. The peripubertal phase starts abruptly around day 40. It is marked by simultaneous events: the appearance of mature Leydig cells in the testis, a striking increase in testosterone and FSH levels, a small rise in LH levels and an acceleration of testicular growth. The phase of rapid growth of seminal vesicle and the first meiotic divisions start around day 70, in presence of high circulating levels of FSH and testosterone. Fighting (3 months) and mounting behaviour (146 ± 13 days) occur lately after a long period of high circulating testosterone levels.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.