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Hum. Reprod. Advance Access published online on August 5, 2005
Human Reproduction, doi:10.1093/humrep/dei194
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© The Author 2005. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.
Received March 3, 2005
Revised May 19, 2005
Accepted June 1, 2005

Article

Effects of the insecticide amitraz, an {alpha}2-adrenergic receptor agonist, on human luteinized granulosa cells

Fiona M. Young 1*, Margaret F. Menadue 2, and Tina C. Lavranos 3

1 Department of Medical Biotechnology, School of Medicine, Flinders University, Adelaide, SA 5042, Australia
2 Endocrinology Unit, Flinders Medical Centre, Adelaide, SA 5042, Australia
3 Department of Obstetrics and Gynaecology, School of Medicine, Flinders University, Adelaide, SA 5042, Australia; Present address: Bionomics Ltd, 31 Dalgleish St, Thebarton, Adelaide, SA 5031, Australia

* To whom correspondence should be addressed.
Fiona M. Young, E-mail: fiona.young{at}flinders.edu.au


  Abstract

BACKGROUND: Amitraz, an insecticide used to prevent tick and mite infestation of cattle, crops and dogs, is an {alpha}2-adrenergic receptor agonist that inhibits GnRH release and the ovulatory LH surge in rats. Noradrenalin, the physiological ligand for adrenergic receptors, inhibits progesterone production by IVF-derived granulosa cells, but the effects of amitraz are unknown. METHODS: Luteinized granulosa cells obtained from women undergoing ovarian stimulation were exposed to amitraz (1, 10, 50, 100 µg/ml) for 2-72 h, and to amitraz (50 µg/ml) ± hCG or the specific {alpha}2-adrenergic receptor antagonist yohimbine, for 6 h. Cell numbers were determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide(MTT) assay and hormone production by radioimmunoassay. RESULTS: Amitraz 10 µg/ml did not affect cell numbers or estrogen production, but reduced progesterone production to 58 ± 8% (p < 0.01, 24 h, n = 6) of control values. Amitraz (100 µg/ml) was cytotoxic and caused a corresponding reduction in hormone production. Amitraz 50 µg/ml did not affect cell numbers or estrogen production, but reduced progesterone per cell production to 82 ± 6% of control values after 6 h. This was prevented by 0.2 mmol/l yohimbine. Exposure to amitraz 50 µg/ml for 6 h exposure abolished hCG-stimulated progesterone production but not estrogen production. CONCLUSIONS: Amitraz inhibited basal and hCG-stimulated progesterone but not estrogen production. The inhibitory action of amitraz and its antagonism by yohimbine suggest that {alpha}2- adrenergic receptors are expressed by luteinized human granulosa cells.

Keywords: {alpha}2-adrenergic receptor/amitraz/human luteinized granulosa cells/reproductive toxicology/steroid hormones.
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