Biological characteristics of the peptides a and β isolated from bovine seminal plasma.

ABSTRACT

The bull seminal plasma peptides a and β have been examined for their biological properties. While both the peptides were able to inhibit the human chorionic gonadotropin-dependent uterine response in the mouse, a alone exhibits the property of suppressing post-castrational rise in gonadotropin in appropriate animal models. This suggests that the peptide β must be acting directly on the ovary to suppress estrogen production and, consequently, the uterine weight increase. Such a possibility was confirmed when a and β were examined by the coupled bioassay which is capable of discriminating between pituitary feedback factors and those acting directly on the gonad. In a test system designed to examine chronic effects, both a and β showed evidence of acting directly on the ovary to inhibit human menopausal gonadotropin-induced estrogen production. Such a direct action could not be correlated with the relative potencies of these peptides when examined for their follicle stimulating hormone-receptor binding inhibitor and lutinizing hormonereceptor binding inhibitor activities.