Meeting Abstract

29.2  Jan. 5  Activity of steroidogenic enzymes in ovary, corpus luteum and placenta of the ringed seal Phoca hispida BLOMQUIST, C.H.*; ATKINSON, S.; BURKANOV, V.N.; GRACHEV, A.I.; University of Minnesota; Alaska SeaLife Center/University of Alaska Fairbanks; Alaska SeaLife Center blomq007@umn.edu

The sites and relative activity levels of steroid-synthesizing enzymes involved in estrogen, androgen and progesterone formation within the maternal-fetal-placental unit during pregnancy in pinnipeds are not well-understood. In this study, 17beta-hydroxysteroid deyhdrogenase (17beta-HSD) activity with estradiol (E₂) and testosterone (T), 3beta-hydroxysteroid dehydrogenase/5-ene-isomerase (3beta-HSD) activity with DHEA, and 3-ketosteroid reductase (3-KSR) activity with 5alpha-DHT were assayed in samples of ovary, CL, placenta and fetal ovary from four reproductive tracts recovered from pregnant ringed seals. The highest levels of each activity (pmol/mg protein) were detected in CL tissue. 3-KSR was the predominant activity in all of the samples, followed by 3beta-HSD. The product of the 3-KSR reaction was 5alpha-androstane-3alpha,17beta-diol. 17beta-HSD activity with E₂ exceeded that with T in CL and ovary in all cases. Activities in fetal ovaries were comparable to those in the maternal ipsilateral ovary lacking the CL. In placenta, 3beta-HSD was near or below the detection limit of our assay, 17beta-HSD activity was detected, as was 3-KSR. Our findings suggest the CL is the major site of 17beta-HSD, 3beta-HSD and 3-KSR activity during the latter stages of pregnancy in P. hispida. Our finding of a predominant 3-KSR activity leading to the formation of 5alpha-androstane-3alpha17beta-diol raises interesting questions as to the possible role of this estrogenic steroid during pregnancy.