Production of a “spawning female‐specific substance” in hepatic cells and its accumulation in the ascites of the estrogen‐treated adult fish, Oryzias latipes

A “spawning female‐specific substance” cross‐reactive with an anti‐chorion glycoprotein antibody is present not only in the ovary but also in the liver and blood plasma of the teleost, Oryzias latipes [Hamazaki et al. (19851, J. Exp. Zool., 235269‐279]. Upon the administration of estrogen, this substance was produced in hepatic cells of both a nonspawning adult female and an adult male. Moreover, a large amount of the substance was accumulated in the ascites fluid that was accumulated in the abdominal cavity of the estrogen fed (EF) fish. The ascites fluid as well as blood plasma of these fish contained also a considerable amount of “probable vitellogenin” (recently identified as real vitellogenin) that showed no cross‐reactivity with the anti‐body. Thus these two substances were major components of the ascites fluid. The antigenic substance, as well as vitellogenin, seems to remain in its native molecular state in the ascites fluid without undergoing enzymatic digestion. On electron microscopic observation of the hepatic cells of the estrogenized male and nonspawning female fish, an unusual formation of electron dense droplets was found among well developed rough‐surfaced endoplasmic reticuli (r‐ER). Immunocytochemical examination revealed that the antigenic substance was localized in the lumen of the r‐ER, Golgi apparatus, some transport vesicles. These results strongly suggest that this “spawning female‐specific substance” is normally produced in the liver under the influence of an estrogenic hormone.