We previously reported that α2-adrenergic agonists enhance absorption and inhibit secretion of electrolytes in small intestine. The present study was undertaken to characterize and localize the relevant receptors. Plasma membranes derived from isolated rabbit ileal epithelial cells was incubated with either [3H]yohimbine (Yo), an α2-antagonist, or p-[3H]aminoclonidine (PAC), an α2-agonist. Scatchard analysis of [3H]Yo binding suggests a single receptor. Competitive displacement of Yo from this receptor by other ligands had a potency order characteristic for α2-receptors in other tissue systems. A Scatchard plot of [3H]PAC binding was curvilinear and best fit by assuming two independent siti. Competitive displacement of [3H]PAC by PAC in the presence of 140 mM Na+ or 0.1 mM GTP increased the IC50 for PAC binding from 10 nM to 100 and 105 nM, respectively, and the Hill coefficient from 0.7 to 1.2 and 1.0, respectively. The ED50 for PAC effect on short-circuit current (200 nM) does not differ significantly from these values. We conclude that α2-receptors are present on ileal enterocytes and that these receptors mediate enterocyte fluid and electrolyte transport function.
|Original language||English (US)|
|Journal||American Journal of Physiology - Gastrointestinal and Liver Physiology|
|State||Published - 1983|
ASJC Scopus subject areas
- Physiology (medical)