Expression and induction of hepatic CYP1A activity in nile tilapia (Oreochromis niloticus) does not appear to be influenced by sexual maturation
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- 作者：Pathiratne ; Asoka ; George ; Stephen G.
- 刊名：Marine Environmental Research
- 出版年：1998
- 出版时间：July 12, 1998
- 年：1998
- 卷：46
- 期：1-5
- 页码：126
- 全文大小：64.4 K
文摘
Previous studies of temperate water fish species which display an annual spawning cycle have demonstrated an estradiol (E2)-dependent suppression in expression of CYP1A activity and inducibility by polycyclic aromatic hydrocarbon (PAH)-type inducers in gonadally mature female fish (Gray <i>et al.i> (1987) <i>Journal of Experimental Zoologyi> 259, 330-342; Lindström-Seppä and Stegeman (1995) <i>Marine Environmental Researchi> 39, 219-223). Many tropical species have a different reproductive strategy and are repeat spawners, e.g. the ovulatory cycle of the common nile tilapia (<i>Oreochromis niloticusi>) can be as short as 15 d providing that brooding is prevented. We have investigated the expression of hepatic CYP1A and its inducibility by a prototypical PAH, 3-methylcholanthrene (3MC) during the spawning cycle of non-brooding females. In these gentically female fish, total hepatic CYP450 levels were significantly lower in gonadally ripe (3-5 d pre-spawn at the peak of plasma E2 levels) and 1 d post-spawn (when E2 levels were lowest) when compared with immature fish or ripe males. Other components of the electron transport system, cytochrome b5, and NADPH-cytochrome c reductase as well as CYP1A activity were not reduced. Northern and western blot analysis and determination of CYP1A-dependent (EROD) activity in livers of immature, gonadally mature male and female, and post-spawn female fish, showed that there was a comparable induction of CYP1A expression in all groups of fish 3 d after 3MC treatment. These data indicate that CYP1A expression does not appear to be regulated by circulatory E2 levels in this species.