ANGIOTENSIN-II AT1 RECEPTORS IN RAT SUPERIOR CERVICAL-GANGLIA - CHARACTERIZATION AND STIMULATION OF PHOSPHOINOSITIDE HYDROLYSIS

Angiotensin II receptor number was higher in superior cervical ganglia of 2-week-old when compared to 8-week-old rats. In both young and adult rats, specific binding of [I-125][Sar1]angiotensin II was displaced competitively by the AT1-receptor antagonist DuP 753 but not by the AT2-receptor competitor PD 123177. In ganglia from adult rats, DuP 753 competed with an IC50 of 113 nM. The stable guanine nucleotide GTP-gamma-S inhibited binding of [I-125][Sar1]angiotensin II in young and adult rats by approximately 50% with IC50 values of 105 and 120 nM, respectively, suggesting that the angiotensin receptor is G-protein linked. Angiotensin II at a dose of 1-mu-M stimulated inositol phosphate formation 58% over control values in superior cervical ganglia from 8-week-old rats. This effect was totally blocked by 10-mu-M DuP 753 but not by 10-mu-M PD 123177. Our findings demonstrate that rat superior cervical ganglia contain AT1-type angiotensin receptors that are probably G-protein linked, and their stimulation results in increased inositol phospholipid metabolism.