The gonadotrophic activity of sera from two mares treated either with human chorionic gonadotrophin or with crude ovine pituitary fsh as antigens has been studied in intact and hypophysectomized immature female and male rats. The studies were projected over a 4-year period during which time the mares were subjected to three and four sequences of immunization, respectively.
One-third millilitre of serum from the mare treated with ovine fsh increases ovarian and uterine weights in intact immature female rats, while 5 ml of serum tends to depress these weights because of the anti-fsh present in the serum. Thirty millilitres of serum approximately doubles the seminal vesicle and prostate weights in intact males, whereas the testis weights are either unaffected or depressed. Based on the ventral prostate responses in Sprague-Dawley hypophysectomized males, the serum is estimated to contain about 25-μg equivalents of nih-lh-s8/ml. Both the serum of this mare and that of an untreated non-pregnant mare depressed the ovarian ascorbic acid level significantly, but the slopes of the responses to graded doses were flat and thus lh values could not be estimated by this procedure.
The biological activity of the serum from the mare treated with hcg as an antigen has been previously described. In earlier studies, Long-Evans hypophysectomized males, operated upon at 23 to 26 days, were used with treatment starting 15 days later. The testes were enlarged but the ventral prostate weights were unaffected by 16 ml of serum. In more recent findings, it has been found that if the animals are operated upon at 21 days and injections begun 4 days later significant ventral prostate weight responses can be obtained with 8 ml of serum. Attempts have been made to separate the gonadotrophic and anti-gonadotrophic activities in this serum by chemical fractionation. From the localization of activities in the γ-globulin fractions of the ammonium sulphate-ethanol procedure, and the α- and β-globulin fractions of the deae-cellulose procedure we conclude that the gonadotrophic and anti-gonadotrophic activities are not following any of the classical serum proteins for which these procedures were devised. It is suggested that most of the contaminating serum proteins could be eliminated by the sequential use of both procedures.