We previously reported that angiotensin II (A-II) enhanced the accessory function of BALF macrophages in some patients with sarcoidosis. We hypothesized that this finding was mediated by the A-II receptor on BALF macrophages. From this viewpoint, we investigated the expression of A-II receptor on BALF macrophages. The binding of 125I-A-II to BALF macrophages was specifically inhibited by unlabeled A-II when incubated for 1 hour at 37 degrees C. However, the uptake of 3H-inulin to BALF macrophages was not inhibited by unlabeled inulin under the same conditions. These findings indicate that the binding of 125I-A-II to BALF macrophages was mediated by the putative A-II receptor, and was not due to pinocytosis.