Hum. Reprod. Advance Access originally published online on August 5, 2005
Human Reproduction 2005 20(11):3018-3025; doi:10.1093/humrep/dei194
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Effects of the insecticide amitraz, an 
2-adrenergic receptor agonist, on human luteinized granulosa cells
1 Department of Medical Biotechnology, School of Medicine, Flinders University, Adelaide, SA 5042, 2 Endocrinology Unit, Flinders Medical Centre, Adelaide, SA 5042 and 3 Department of Obstetrics and Gynaecology, School of Medicine, Flinders University, Adelaide, SA 5042, Australia 4 Present address: Bionomics Ltd, 31 Dalgleish St, Thebarton, Adelaide, SA 5031, Australia
5 To whom correspondence should be addressed. E-mail: fiona.young{at}flinders.edu.au
BACKGROUND: Amitraz, an insecticide used to prevent tick and mite infestation of cattle, crops and dogs, is an 
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 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 2- adrenergic receptors are expressed by luteinized human granulosa cells.
Key words:
2-adrenergic receptor/amitraz/human luteinized granulosa cells/reproductive toxicology/steroid hormones