Melatonin, but not somatostatin-14 influences in vitro steroidogenesis by ovarian follicles of rainbow trout |
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| Authors: | PK Reddy AC Holloway R Renaud JF Leatherland |
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| Institution: | (1) Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, N1G 2W1, Canada |
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| Abstract: | Ovarian follicles taken from sexually maturing rainbow trout at the mid-vitellogenic stage of ovarian development were incubated in vitro in the presence or absence of melatonin or somatostatin-14 (SRIF-14) to determine whether there is evidence of a direct action of these factors on gonadal steroidogenesis in fishes. The steroidogenic capacity of the ovarian follicles was assessed by measuring testosterone (T) and 17 -estradiol (E2) release into the incubation medium, and by examining the steroid metabolites produced following incubation of follicles with radiolabelled steroid precursors.Melatonin appears to elicit a biphasic effect on steroidogenesis by in vitro rainbow trout ovarian follicles; at a concentration of 1 × 10–3 M, melatonin stimulated basal T and E2 production, but at a concentration of 1 × 10–2 M there was an inhibition of basal and sGtH-stimulated T and E2 Melatonin may act to reduce the activity of specific steroidogenic enzymes, since there was evidence of melatonin at 1 × 10–2 M enhancing the accumulation of 3H]17 -hydroxyprogesterone in the medium following incubation with 3H]pregnenolone, possibly suggesting the inhibition of C17,20-lyase activity. In contrast, SRIF-14, used at concentrations of 1 × 10–8 M and 1 × 10–6 M, had no effect on basal or sGtH-stimulated E2 or T production by ovarian follicles, incubated in vitro. |
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| Keywords: | androstenedione 17 -estradiol" target="_blank">gif" alt="beta" align="MIDDLE" BORDER="0">-estradiol granulosa cells 17 -hydroxyprogesterone" target="_blank">gif" alt="agr" align="BASELINE" BORDER="0">-hydroxyprogesterone Oncorhynchus mykiss ovary testosterone theca cells |
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