Meeting Abstract

87.10  Thursday, Jan. 7  The regulatory role of sex steroids during primary growth of ovarian follicles of coho salmon (Oncorhynchus kisutch) FORSGREN, K.L.*; YOUNG, G.; Univ. of Washington klforsg@u.washington.edu

Studies on the endocrine regulation of oogenesis in teleosts have primarily focused on the later (secondary growth: vitellogenesis and maturation) stages of oocyte development. The regulation of earlier stages of development (primary growth: from chromatin nucleolar stage to cortical alveoli stage) is poorly understood and is of interest because aspects of fecundity and egg quality are thought to be determined during this time. We have developed an in vitro model based on long-term culture of ovarian follicles of coho salmon (Oncorhynchus kisutch). Our research to date indicates that sex steroids regulate the early stages of ovarian development, particularly the perinucleolar stage. Late perinucleolar ovarian follicles were cultured with various doses of estradiol-17beta (E2), testosterone (T), or 11-ketotestosterone (11KT) and then analyzed by histology. After 7 days, the highest dose of E2 (30 ng/ml) had only minor effects on oocyte volume. However, long-term culture (21 days) at the same dose resulted in the accumulation of cortical alveoli. 11-KT, a non-aromatizable androgen, significantly stimulated the growth of late perinucleolar oocytes compared to controls even at the lowest dose (0.03 ng/ml). T also stimulated oocyte growth, but was much less effective than 11-KT. Long-term culture with high doses of T (3 and 30 ng/ml) also resulted in the accumulation of cortical alveoli similar to E2. Overall, these results suggest that androgens may be primarily responsible for stimulating growth during the late perinucleolar stage, whereas E2 may be involved in the stimulation of cortical alveoli synthesis. (Supported by National Research Initiative Competitive Grant No. 2003–35203-13602 from the USDA Cooperative State Research, Education and Extension Service)