RX781094 a potent and selective alpha 2-adrenergic antagonist. Effects in adipocytes and hepatocytes

The potency and selectivity of RX781094, 2-(2-(1,4-benzodioxanyl]-2-imidazoline HCl, as alpha 1- and alpha 2-adrenergic antagonist was studied using rat hepatocytes and hamster adipocytes. The alpha 1-adrenergic stimulation of ureogenesis produced by epinephrine in rat hepatocytes was slightly diminished by 10(-4) M RX781094. On the contrary the alpha 2-adrenergic effect of epinephrine in hamster adipocytes (inhibition of adenylate cyclase) was antagonized dose-dependently by RX781094. This agent was approximately 10-fold more potent than yohimbine. Radioligand binding studies also showed that RX781094 was more potent and selective than yohimbine at alpha 2-adrenergic sites. It is concluded that RX781094 is a potent and selective alpha 2-adrenergic antagonist.