Hormonal and immunological aspects of sex steroid-binding plasma protein of primates.

Sex steroid-binding plasma protein binds dihydrotestosterone, testosterone, and oestradiol with high affinity (Kd,eq. approximately 0.5, 1 and 2 nM, respectively), in man (h-SBP) and in monkeys. Steroid-binding specificity is identical in all primates. However oestrone does not displace dihydrotestosterone binding in man or chimpanzee. Gel filtration experiments and immunoelectrophoretic analysis with a mono-specific antiserum raised in the rabbit against h-SBP indicate cross-reactivity with primate SBPs (from complete in chimpanzee and gorilla to weak in prosimians), but no cross-reaction with other mammalian androgen-binding plasma proteins.