[Mechanism of vascular desensitization to agonists]

The patterns and mechanism of vascular desensitization to agonists were studied in isolated arteries of Wistar and SHR rats. The results showed that: (1) Arteries were much easier to desensitize peptidergic agonists (A II, AVP) than catecholaminer gic agonists (NE, PE); (2) the desensitization induced by peptidergic agonists and catecholaminer gic agonists were homologous within 30 minutes; (3) the endothelium-EDRF-cGMP pathway was not involved in agonist-induced desensitization; (4) inhibition of surface receptor internalization by phenylarsine oxide (PAO, 10(-5)mol/L) could transiently reverse the desensitization and the blocking of intracellular receptor re-insertion into the membrane by chloroauine (10(-5)mol/L) could accelerate the desensitization in varying degrees with different arteries, which demonstrated the involvement of receptor cycling in homologous desensitization, but was not the unique mechanism; (5) there was no change in the function of voltage-dependent Ca2+ channel during homologous desensitization; (6) the concentration-contraction curve of GTP gamma S shifted down-ward during homologous desensitization, suggesting the functional change of G protein (s); (7) the desensitization to agonists didn't decrease in arteries of SHR compared with the arteries of Wistar rats.