Peripheral concentrations of gonadotropins and progestins during pregnancy in rabbits after active immunization against testosterone

The effects of active immunization of female rabbits against testosterone on various endocrine parameters during pregnancy were examined. Peripheral blood samples were obtained from immunized rabbits at timed intervals after mating up to the 29th day of pregnancy, when the rabbits were killed and various tissues were analyzed. Progesterone concentrations were higher in testosterone-immunized rabbits (TIR) than in controls during pregnancy. Luteinizing hormone (LH) and follicle-stimulating hormone concentrations were not significantly different in controls and TIR during pregnancy. Both progestins and gonadotropins showed the expected coitus-induced increases, but LH levels were higher in TIR. The binding of testosterone in fetal plasma and amniotic fluid was higher in TIR than in controls. Weights of fetuses and litter size were not significantly different in TIR and controls. These data suggest that testosterone may play a role during pregnancy in the rabbit

Effects of active immunization of female rabbits against testosterone

Prepubertal (immature) and mature female rabbits were actively immunized against testosterone-3-oxime-bovine serum albumin over a period of 11 weeks. The antibody titre was significant in all animals by 5 weeks. The concentration of FSH in prepubertal animals decreased significantly (P less than 0.001) between weeks 1 and 5, but no significant changes were observed in the concentration of LH at any time. After immunization for 8 weeks, there was a significant (P less than 0.05) increase in the serum concentration of androgen and the percentage of bound testosterone also increased (P less than 0.05). The serum concentration of oestradiol increased after immunization for 11 weeks, compared with values at 8 weeks (P less than 0.05) and oestradiol binding also rose by week 5 (P less than 0.01). Libido was not affected and significantly (P less than 0.005) increased numbers of ovulations were noted in immunized animals. These results suggest that immunization of the female rabbit against testosterone may disrupt the normal regulation of follicular maturation

Adenosine triphosphate inhibits LH stimulated testosterone accumulation by isolated rabbit ovarian follicles

Testosterone is a major secretory product of the rabbit follicle. Work from our laboratory also suggests that the steroidogenic responses of the follicles to LH and cAMP are different in that the LH effects were more long lasting whereas the response to cAMP could be evoked at will. Cyclic AMP is accepted as the second messenger which mediates the steroidogenic response to LH. It was therefore of interest to determine whether different responses could be elicited when LH and nucleotides were added together to isolated rabbit follicles. Unless otherwise stated procedures used were similar to those previously described. It was not determined whether ATP inhibited the binding of LH to the follicular cells. This possibility must be considered since the binding of HCG to bovine corpora lutea membranes can be inhibited by nucleotides. Although ATP could have inhibited LH binding it is apparent that this inhibition is not complete since testosterone production could be observed after the ATP was removed (panel e, final 2 h of incubation). The resumption of steroidogenesis after the removal of ATP is similar to data obtained with inhibitors of protein synthesis and lends further support to our contention that LH binding to follicular cells initiates an irreversible series of events which can be delayed at sites beyond gonadotropin binding, by various inhibitors. Testosterone is a major secretory product of the rabbit follicle. Work from our laboratory also suggests that the steroidogenic responses of the follicles to LH and cAMP are different in that the LH effects were more long lasting whereas the response to cAMP could be evoked at will. Cyclic AMP is accepted as the second messenger which mediates the steroidogenic response to LH. It was therefore of interest to determine whether different responses could be elicited when LH and nucleotides were added together to isolated rabbit follicles. Unless otherwise stated procedures used were similar to those previously described. It was not determined whether ATP inhibited the binding of LH to the follicular cells. This possibility must be considered since the binding of HCG to bovine corpora lutea membranes can be inhibited by nucleotides. Although ATP could have inhibited LH binding it is apparent that this inhibition is not complete since testosterone production could be observed after the ATP was removed (panel e, final 2 h of incubation). The resumption of steroidogenesis after the removal of ATP is similar to data obtained with inhibitors of protein synthesis and lends further support to our contention that LH binding to follicular cells initiates an irreversible series of events which can be delayed at sites beyond gonadotropin binding, by various inhibitor