Effects of the insecticide amitraz, an α2-adrenergic receptor agonist, on human luteinized granulosa cells

Abstract

Background: Amitraz, an insecticide used to prevent tick and mite infestation of cattle, crops and dogs, is an α2-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 α2-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 α2- adrenergic receptors are expressed by luteinized human granulosa cells. © The Author 2005. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.