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.

Endogenous endothelin increases gallbladder tone and leads to acute cholecystitis in the Australian possum.

Endothelins are bioactive peptides produced by gallbladder epithelial cells. We aimed to determine the role of endothelins in acute cholecystitis. Escherichia coli lipopolysaccharide vs saline (sham) was instilled into the gallbladder lumen of Australian possums.

Increased thirst and vasopressin secretion after myocardial infarction in rats.

Impaired regulation of salt and water balance in left ventricular dysfunction and heart failure can lead to pulmonary and peripheral edema and hyponatremia. Previous studies of disordered water regulation in heart failure have used models of low cardiac output with normal cardiac function (e.g.

Endothelin ETA receptor antagonism does not attenuate angiotensin II-induced cardiac hypertrophy in vivo in rats.

1. Angiotensin (Ang) II causes cardiac hypertrophy in vitro and in vivo. It also stimulates the release of endothelin (ET)-1.

Prostaglandin F2 alpha mediates platelet-activating factor-stimulated atrial natriuretic factor release from the isolated rat heart.

Platelet-activating factor (PAF) and the prostaglandins have recently been shown to stimulate atrial natriuretic factor (ANF) secretion from the heart. As PAF also potentiates the release of cyclooxygenase products from isolated hearts, the role of these substances in PAF-induced ANF secretion was investigated. Using an isolated perfused rat heart preparation, cyclooxygenase inhibition by indomethacin or meclofenamic acid (10 microM for each) significantly attenuated the rise in ANF associated with PAF administration (2.