Effects of the insecticide amitraz, an alpha2-adrenergic receptor agonist, on human luteinized granulosa cells.
BACKGROUND
Amitraz, an insecticide used to prevent tick and mite infestation of cattle, crops and dogs, is an alpha2-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 microg/ml) for 2-72 h, and to amitraz (50 microg/ml) +/- hCG or the specific alpha2-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 microg/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 microg/ml) was cytotoxic and caused a corresponding reduction in hormone production. Amitraz 50 microg/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 microg/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 alpha2-adrenergic receptors are expressed by luteinized human granulosa cells.
Young
Fiona M
FM
Department of Medical Biotechnology, School of Medicine, Flinders University, Adelaide, SA 5042, Australia. fiona.young@flinders.edu.au
Menadue
Margaret F
MF
Lavranos
Tina C
TC
D058647:Adrenergic alpha-2 Receptor Agonists; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D003864:Depression, Chemical; D004967:Estrogens / Q000096:biosynthesis; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007306:Insecticides / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000502:physiology; D011374:Progesterone / Q000096:biosynthesis; D014052:Toluidines / Q000494:pharmacology*; D015016:Yohimbine / Q000494:pharmacology
D058647:Adrenergic alpha-2 Receptor Agonists; D006063:Chorionic Gonadotropin; D004967:Estrogens; D007306:Insecticides; D014052:Toluidines; D015016:Yohimbine; C014983:amitraz; D011374:Progesterone; D007986:Luteinizing Hormone