期刊
GENERAL AND COMPARATIVE ENDOCRINOLOGY
卷 117, 期 2, 页码 260-267出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1006/gcen.1999.7416
关键词
vitellogenesis; ovary; steroidogenesis; vitellogenin; rainbow trout
In vivo and in vitro the concentration of vitellogenin (VTG) inside the oocyte can alter VTG production by the liver, modulating the synthesis of 17 beta-estradiol (E-2) by the ovary. To gain a greater insight into this mechanism, the in vitro production of free and conjugated testosterone (T), E-2, and androstenedione (A) by rainbow trout oocytes from the early and middle vitellogenic stage was measured by radioimmunoassay. There was a decreased E-2 production that was greater in September (40%) than October (30%), by the oocytes incubated with the vitellogenic fraction. The production of E-2 conjugated as glucuronide was lower than sulfate (P < 0.05), but similar in control and VTG-incubated oocytes. levels of free T increased from September to October, and conjugates were both produced at low levels, and no differences were detected between control and incubated VTG oocytes. The decreased synthesis of E-2 by oocytes incubated with VTG was not followed by an increase in the amount of T or conjugated E-2, because there were no differences under the two circumstances. However, there was a reduced synthesis of A with oocytes producing low levels of E-2. These results suggest that the presence of high levels of VTG in the oocyte suppresses the synthesis of A and E-2, affecting the activities of the enzymes C17,20 lyase and aromatase and probably interfering with the heme protein cytochrome P450 which in the ovary catalyses C 17,20 lyase (P450 c17) and aromatase (P450arom). (C) 2000 Academic Press.
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