Early sex differences in hormonal potentialities of gonads from quail embryos with a sex-linked pigmentation marker: an in vitro radioimmunoassay study.

Quail embryos with a sex-linked eye pigmentation marker allowing sex identification at autopsy provided a biological model for radioimmunoassay of sex steroids in embryonic quail gonads at a very early stage (51/2 and 61/2 days). The purpose was to demonstrate a sex difference in hormonal potentialities of the gonads before any morphological indication of sexual differentiation. Evidence of early steroidogenesis by undifferentiated gonads could be obtained: estrogen synthesis characterized female gonads, while testosterone was produced by the gonads of both sexes. The sex hormonal production was concomitant with, or even preceded, the apparent beginning of sex differentiation of gonads.