CHARACTERIZATION OF AT2 ANGIOTENSIN-II RECEPTORS IN RAT ANTERIOR CEREBRAL-ARTERIES

Quantitative autoradiography using the agonist I-125-Sar1-angiotensin II was used to localize and characterize angiotensin II (AT) receptors in the anterior cerebral artery of the male rat. This artery showed a moderately high number of AT receptors, localized throughout the arterial wall. The number of receptors was higher (125 +/- 7 fmol/mg protein) in arteries from young 2-wk-old rats compared with those in adult 8-wk-old rats (43 +/- 2 fmol/mg protein). In the anterior cerebral artery, AT binding was insensitive to displacement with the selective AT1 antagonist DuP 753 but was readily displaced by the selective AT2 antagonist CGP-42112 A (concentration eliciting 50% of maximum inhibition: 6 +/- 1 x 10(-10) M). This indicated that the AT receptors in the cerebral artery were of the AT2 subtype. Our observations suggest that AT may exert its effects on cerebral circulation by stimulation of AT2 receptors and that these receptors may play a role during cerebrovascular development.