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Suzanne Gronen,¹ Nancy Denslow,² Steve Manning,¹ Sue Barnes,¹ David Barnes,¹ and Marius Brouwer¹

¹University of Southern Mississippi, Institute of Marine Sciences, Department of Coastal Sciences, Ocean Springs, MS 39564 USA
²University of Florida, Gainesville, FL 32610 USA

Abstract

The induction of synthesis of the "female" yolk precursor protein vitellogenin (VTG) in male fish by estrogenic chemicals in the environment has been demonstrated in many recent reports. However, little is known about the organismal and biological significance of this phenomenon. To examine the relationship between VTG production in male fish and reproductive impairment, adult male medaka were exposed to 4-tert-octylphenol (OP) , a known environmental estrogen, in concentrations ranging from 20 to 230 ppb for 21 days, under flow-through conditions. Following exposure, male fish were mated, in the absence of OP, with unexposed females. Breeding groups composed of exposed males and control females produced about 50% fewer eggs than control groups. VTG levels in serum of male fish increased with increasing OP exposure concentration and decreased after OP exposure was discontinued. Nevertheless, significant correlations (p<0.01) were observed between VTG levels in exposed male fish and 1) OP exposure concentrations, 2) percent of fertilized eggs, and 3) survival of embryos. OP-induced VTG synthesis and reproductive impairment appear to be closely linked phenomena. Histological examination indicated spermatogenesis in OP-exposed fish was inhibited, and some exposed fish had oocytes in their testes. Finally, OP caused a significant increase in the number of abnormally developing embryos, suggesting that OP may be genotoxic as well as estrogenic. Key words: medaka, octylphenol, reproduction, vitellogenin, xenoestrogen. Environ Health Perspect 107:385-390 (1999) . [Online 2 April 1999]

http://ehpnet1.niehs.nih.gov/docs/1999/107p385-390gronen/ abstract.html

Address correspondence to M. Brouwer, Institute of Marine Sciences, Department of Coastal Sciences, University of Southern Mississippi, 703 East Beach Drive, Ocean Springs, MS 39564 USA.

We thank Jeffrey Lotz for help with statistical analysis and Nancy Brown-Peterson and Rena Krol for histological advice.

This study was supported in part by the Mississippi- Alabama Sea Grant Consortium grant award NA86RG0039. S.G. was supported by a USM master's research assistantship.

Received 4 November 1998 ; accepted 25 January 1999.