Steroid release from separated theca and granulosa layers of Atlantic salmon (Salmo salar) ovarian follicles: the effects of a purified salmon gonadotrophin preparation |
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| Authors: | R S Wright Wei-xin Zhao |
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| Institution: | (1) Department of Agriculture and Fisheries for Scotland, Marine Laboratory, Victoria Road, PO Box 101, AB9 8DB Aberdeen, Scotland;(2) Department of Aquaculture, Shanghai Fisheries College, 334 Jun-gong Road, Shanghai, China |
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| Abstract: | Theca and granulosa layers were removed from ovarian follicles of mature Atlantic salmon (Salmo salar) and were separately incubated under sterile conditions with and without a partially purified salmon gonadotrophin preparation (GTH). Aliquots of the incubation media were removed at intervals and analysed for the steroids 17 , 20 -dihydroxy-4-pregnen-3-one (1720P), 17-hydroxyprogesterone, progesterone, androstenedione, testosterone and oestradiol. The biosynthesis of C19 and C21 steroids was very largely restricted to the thecal tissue and was markedly stimulated in the presence of GTH. Androstenedione (max 65 ng/ml) and testosterone (max 14 ng/ml) were released from the earliest stages of incubation whereas the release of 17-hydroxyprogesterone (max 51 ng/ml) and progesterone (max 5.5 ng/ml) commenced only after a lengthy induction period. A trace (1.0 ng/ml) of 1720P was produced by the theca in the presence of GTH but oestradiol was not detected. The granulosa preparations released levels of 17-hydroxyprogesterone and androstenedione only marginally above the detection limits (ca 0.7 ng/ml) and there was little stimulation of output with GTH. Oestradiol (max 4 ng/ml) was released only in the presence of GTH. 1720P, progesterone and testosterone were not detected as products of this tissue. These results, together with those derived earlier from incubations of complete follicles support the view that the synthesis of 1720P is essentially a two-cell process in which 17-hydroxyprogesterone produced in the theca is subject to the action of steroid 20-hydroxysteroid dehydrogenase in the granulosa. The temporal pattern of release of steroids in these and earlier experiments is considered in relation to mechanisms of steroid biosynthesis and to their possible roles in oocyte final maturation. |
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| Keywords: | salmon Salmo salar ovarian follicles granulosa theca steroids gonadotrophin |
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