Autoradiographs showing the effects of unlabeled ANG II (10 μM) and losartan (10 μM) on specific AT4 receptor binding in the rat kidney. AT4 receptors were labeled by 125I-Nor-Leu-ANG IV, a selective agonist for ANG IV. Note that unlabeled native ANG IV (B, 10 μM) and the antagonist divalinal-ANG IV (C, 10 μM) displaced most AT4 receptor binding. AT4 receptor binding was also displaced to a significant extent by unlabeled ANG II (D) or losartan (E, 10 μM) but not by PD-123319 (F, 10 μM).