Production and metabolic clearance of angiotensinogen in conscious rats as measured by steady-state isotope dilution.
Previous studies on the hormonal regulation of hepatic angiotensinogen relied on in-vitro liver preparations and on the measurement of changes in plasma concentration. In this study 125I-labelled angiotensinogen was used to measure simultaneously the production rate (PR) and metabolic clearance rate (MCR) in conscious rats by the constant-rate infusion and single-injection methods. Male rats received daily s.c. injections of isotonic saline (as control), 1 mg corticosterone acetate (CA), 25 micrograms 17 beta-oestradiol benzoate (OB) or 20 micrograms thyroxine (T4) per 100 g body weight. On day 7 of treatment 125I-labelled angiotensinogen was infused into a jugular vein at a rate of 1 microliter/h by osmotic minipumps and blood samples taken 4, 5 and 6 days later. The PR of angiotensinogen increased from 576 +/- 28 (S.E.M.; n = 9) to 954 +/- 63 (n = 9), 1010 +/- 84 (n = 9) and 2359 +/- 150 (n = 10) micrograms/h per kg following treatment with CA, OB and T4 respectively. In contrast, the PR of rat albumin did not change significantly from 218 +/- 8 (n = 7) mg/h per kg. All three hormones increased MCR from 13 +/- 1 (n = 17) ml/h per kg to 17 +/- 1 (n = 9), 18 +/- 2 (n = 9) and 27 +/- 2 (n = 9) ml/h per kg for CA, OB and T4 respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
D000808:Angiotensinogen / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D003345:Corticosterone / Q000031:analogs & derivatives / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D007457:Iodine Radioisotopes; D008297:Male; D008657:Metabolic Clearance Rate / Q000187:drug effects; D011865:Radioisotope Dilution Technique; D051381:Rats; D011919:Rats, Inbred Strains; D013974:Thyroxine / Q000494:pharmacology
D007457:Iodine Radioisotopes; D000808:Angiotensinogen; D004958:Estradiol; C029939:corticosterone acetate; D013974:Thyroxine; D003345:Corticosterone