Using Chinese Hamster Ovary cells expressing human AT 1 receptors cells (CHO-hAT 1 ), it was previously shown that insurmountable inhibition of the angiotensin II response by non-peptide antagonists is related to the duration of their receptor occupancy. In the present study it was shown that these antagonists displayed similar binding characteristics to endogenously expressed AT 1 receptors in human adrenal cortex cells (NCI-h295) and renal vascular smooth muscle cells (HVSMC). Competition binding studies with [ 3 H]candesartan for NCI-h295 cells, with [ 1 2 5 I]Sar 1 -Ile 8 angiotensin II for HVSMC and with both radioligands for CHO-hAT 1 cells displayed the same potency order for unlabelled antagonists: candesartan>EXP3174>irbesartan>losartan. The AT 2 receptor antagonist PD123319 displayed low potency in all instances. The apparent half-lives of the antagonist-AT 1 receptor complexes in NCI-h295 cells and HVSMC were comparable to those obtained under identical conditions with CHO-hAT 1 cells. Angiotensin II increased the inositol phosphate accumulation dose dependently with half-maximal response at 17.4+/-1.6nM for NCI-h295 cells and 4.5+/-0.8nM for HVSMC. Pre-incubation of the cells with losartan only produced concentration-dependent rightward shifts of the angiotensin II concentration-response curve. The maximal response was decreased by 85-92% with candesartan, 70-88% with EXP3174 and 60% with irbesartan. The similar binding and inhibitory properties of these antagonists among the investigated cell types validates the use of CHO-hAT 1 cells for investigating pharmacological properties of human AT 1 receptors.