ANGIOTENSIN AT(2) RECEPTOR DEGRADATION IS PREVENTED BY LIGAND OCCUPATION

A substantial increase in [I-125]Sar(1),Ile(8)-Angiotensin II binding activity can be observed 24 hours after treatment of R3T3 cells with A T(2) receptor agonists and antagonists. An increase in the radioligand binding activity, although less profound, can also be observed 6 hour s after AT(2) receptor ligand treatment, on fetal human kidney cells e xpressing a recombinant human AT(2) receptor. However, the increase in radioligand binding activity cannot be detected unless the ligands ar e removed from the cell surface by an acid-glycine (pH 3) wash, just p rior to the binding assay. Interestingly, an acid-glycine wash 24 hour s prior to the binding assay causes a dramatic decrease in the radioli gand binding activity on untreated R3T3 cells. This decrease, which wa s prevented by angiotensin II treatment, suggests the existence of an unknown endogenous factor which, like the AT(2) receptor ligands, seem s to prevent AT(2) receptor degradation. (C) 1998 Academic Press.