title: Autopotentiation of pressor responses by subpressor angiotensin II in rats.
abstract: The mechanisms whereby the continuous administration of initially subpressor doses of angiotensin II (ANG II) leads to pressor hyperresponsiveness and gradual development of hypertension were investigated. Male Sprague-Dawley rats (350 to 400 g) were given ANG II intraperitoneally, 200 ng/kg/min, for 24 h, 7 to 10 days, or 6 weeks. Vehicle-infused rats were controls. Pressor responses to incremental doses of ANG II, norepinephrine (NE), and serotonin were measured in chloralose-anesthetized rats, before and after neurohumoral blockade, and the main findings were confirmed in awake, free-moving rats with implanted catheters. Pressure responses to ANG II and NE were also measured in the isolated, pump-perfused mesenteric circulation of rats after 7 to 10 days of ANG II or sham infusion. Compared with control rats, there were no hemodynamic changes in ANG II-treated rats at 24 h. After 7 to 10 days of ANG II treatment, tail systolic blood pressure rose by 13 mm Hg (P < .01) and pressor responses to ANG II (P < .01) but not to NE or serotonin were increased. Pressor hyperresponsiveness was due in part to potentiation of vascular responses because pressure responses to ANG II (P < .002) but not to NE were also increased in the mesenteric circulation of ANG II-treated rats. By 6 weeks, mild hypertension was well established in ANG II-treated rats and pressor responses were increased to both ANG II (P < .05) and NE (P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, Veterans Affairs Medical Center, Minneapolis, MN 55417.
authors.forename: G
authors.initials: G
authors.lastname: Abraham
authors.forename: G
authors.initials: G
authors.lastname: Simon
mesh_terms: D000595:Amino Acid Sequence; D000758:Anesthesia; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D002698:Chloralose; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000503:physiopathology; D007274:Injections, Intraperitoneal; D008297:Male; D008969:Molecular Sequence Data; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012083:Renin / Q000097:blood; D012701:Serotonin / Q000494:pharmacology; D013152:Splanchnic Circulation / Q000187:drug effects; D014667:Vasopressins / Q000097:blood
chemical_list: D014667:Vasopressins; D000804:Angiotensin II; D002698:Chloralose; D012701:Serotonin; D012083:Renin; D009638:Norepinephrine