title: Estimation of regional metabolism and production of angiotensins in hypertensive subjects.
abstract: 1. We attempted to collect information on the metabolism and production of angiotensins (ANG) in different vascular beds in humans by constant i.v. infusion of mono-iodinated [125I]-ANG I into subjects with essential hypertension, at the time of renal vein catheterization as part of the diagnostic work-up for renovascular hypertension. 2. Blood samples were taken from the aorta and the renal, antecubital, femoral and hepatic veins. ANG I, ANG II, [125I]-ANG I and [125I]-ANG II were extracted from plasma, separated by h.p.l.c. and quantitated by radio-immunoassay or gamma counting. 3. Our studies so far are restricted to subjects on captopril 50 mg twice daily. Under ACE inhibition (4-6 h after dosing of captopril) no differences in elimination half-life and regional extraction were found between infused [125I]-ANG and unlabelled ANG I. Extraction of arterially delivered [125I]-ANG I was 80% in the kidney, 45% in the forearm, 58% in the leg and 95% in the hepato-mesenteric vascular bed. 4. Measurements of arterial and venous [125I]-ANG II levels indicated that [125I]-ANG I-II conversion had occurred in the cardio-pulmonary vascular bed. 5. ANG I production in the hepato-mesenteric region could be largely accounted for by the renin activity of circulating plasma, but in kidney and limbs only 20-30% of regionally produced ANG I could be accounted for by plasma renin activity. 6. Thus, a major fraction of regionally produced ANG I appears to be formed locally, i.e. not in circulating plasma.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Internal Medicine I, University Hospital Dykzigt, Erasmus University, Rotterdam, The Netherlands.
authors.forename: M A
authors.initials: MA
authors.lastname: Schalekamp
authors.forename: P J
authors.initials: PJ
authors.lastname: Admiraal
authors.forename: F H
authors.initials: FH
authors.lastname: Derkx
mesh_terms: D000328:Adult; D000803:Angiotensin I / Q000008:administration & dosage / Q000096:biosynthesis / Q000097:blood; D000804:Angiotensin II / Q000096:biosynthesis / Q000097:blood; D000809:Angiotensins / Q000097:blood*; D001158:Arteries; D001769:Blood / Q000378:metabolism; D006801:Humans; D006973:Hypertension / Q000097:blood*; D007262:Infusions, Intravenous; D007457:Iodine Radioisotopes; D008875:Middle Aged; D014680:Veins
chemical_list: D000809:Angiotensins; D007457:Iodine Radioisotopes; D000804:Angiotensin II; D000803:Angiotensin I