Regional differences in the functional and biochemical properties of endothelin receptor subtypes in the rabbit prostatic urethra

摘要: OBJECTIVE To examine the regional differences in functional (pharmacological) and biochemical properties of endothelin (ET) receptors rabbit prostatic urethra. MATERIALS AND METHODS The ET 6-month-old male urethras were examined using isolated muscle-bath radioligand receptor-binding techniques. Using plasma membrane suspensions, saturation inhibition experiments with [125I]ET-1 unlabelled agonists antagonists (ETA-selective antagonist BQ123, ETB-selective agonist sarafotoxin 6c, STX6c) done to determine receptor densities their subtype specificities different regions urethra. RESULTS The ETs (ET-1 ET-3) produced significant concentration-dependent contractile responses smooth muscle strips from urethra. Although maximum induced by ET-1 similar regions, ET-3 greater distal region than proximal or middle suggesting that response is more potent all there are region-specific but not ET-1. Moreover, ET-3-induced was suppressed BQ788 (a selective ETB receptor) contributes mediated ET-3. The expressed higher concentrations regions. BQ123 STX6c inhibited binding high low affinity constants, indicating presence both ETA subtypes. proportions high-affinity sites for representing receptors, ≈ 68%, 63% 42% proximal, respectively. By contrast, STX6c, ≈ 27%, 35% 52% middle, These data indicate subtypes, existence urethra. CONCLUSION The results suggest subtypes mediate ET-3, reflecting