Endothelin ETA and ETB receptors in postnatal intestine

We aimed to characterize endothelin (ET) receptors in the swine intestinal vasculature and to determine ischemia-reperfusion (I/R) effects on these re ceptors. Saturation and competitive binding assays were performed on mesent eric artery protein membranes from 1- and 40-day-old animals, both control and those subjected to 1 h of partial ischemia followed by 6 h of reperfusi on in vivo. Scatchard analysis of saturation binding with I-125-labeled ET- 1 in membranes from endothelium-denuded (E-) vessels revealed that the maxi mum number of binding sites was greater in younger animals. Competitive I-1 25-ET-1 binding was significant for a one-site model with ET-1, ET-3, and s arafotoxin S6c (S6c) in membranes from endothelium-intact (E+) and E- vesse ls in both age groups. The maximum number of ET-1 binding sites was signifi cantly greater in younger animals. In the presence of the ETA receptor anta gonist BQ-123, competitive I-125-ET-1 binding was significant for a one-sit e model with ET-1 and S6c in membranes from E+ vessels in both age groups. The maximum number of ET-1 binding sites was significantly greater in young er animals. After I/R, the maximum number of ET-1 binding sites was unchang ed. In the presence of BQ-123, specific binding by ET-1 and S6c was elimina ted in both age groups after I/R. These results suggest that both ET recept or populations are expressed to a greater degree in younger animals and I/R significantly affects the ETB receptor.