Synchronous production of the low- and high-molecular-weight precursors of the egg envelope subunits, in response to estrogen administration in the teleost fish Oryzias latipes.

Estrogen stimulation of production and accumulation of L-SF and H-SF, the low- and high-molecular-weight precursors of the egg envelope subunits in Oryzias latipes, was analyzed by immunohistochemical and immunoblotting methods. Both SF substances were detected in the liver of the male fish as quickly as 16-24 hr after estrogen treatment, and their production and accumulation in the liver and blood plasma increased as estrogen treatment continued. Immunohistochemical analysis revealed that the number of cells producing both SF substances was increased in the liver as estrogen treatment continued. These results strongly suggest the occurrence of synchronous production of L-SF and H-SF in response to estrogen. In liver extracts, but not in blood plasma, an additional L-SF-like immunoreactive protein was detected on immunoblots. Preliminary data indicate parallel appearance of vitellogenin and SF substances in the liver of estrogenized fish.