Department of Marine Science and Resources, College of Bioresource Sciences, Nihon University, Fujisawa, Kanagawa 252-8510, Japan
The activities of P450 aromatase (P450arom), which converts androgens into estrogens, were measured in ovarian and brain tissues of 9 teleost species; Chasmichthys dolichognathus, Leucopsarion petersii, Acanthogobius flavimanus (Gobiidae), Oncorhynchus mykiss, O. kisutch (Salmonidae), Takifugu niphobles (Tetraodontidae), Rudarius ercodes (Monacanthidae), Enneapterygius etheostomus (Tripterygiidae), and Oryzias latipes (Adrianichthyidae). Ovarian follicle and brain tissue samples were taken from yolk-accumulating mature females of each species. Cell free homogenate was prepared from each sample, and incubated with [1β-3H] androstenedione as a substrate. Radioactivities of free-3H2O were measured and P450arom activities were calculated. Ovarian follicle tissues of C. dolichognathus, L. petersii, A. flavimanus, and O. mykiss represented high P450arom activity followed by O. kisutch. Conversely, ovarian follicle tissues of T. niphobles, R. ercodes, E. etheostomus, and O. latipes, exhibited relatively low P450arom activities. P450arom activities of brain tissues did not differ greatly among species. The activities were, therefore, higher in the ovary than in the brain in the former five species, and vice versa in the latter four species.