Hepatic conversion of angiotensin I and the portal hypertensive response to angiotensin II in normal and regenerating liver.
OBJECTIVE
Angiotensin I (AI) and angiotensin II (AII) induce a portal hypertensive response (PHR) and the liver is able to convert AI into AII to trough the action of the angiotensin-converting enzyme (ACE). Our purpose was to characterize angiotensin I liver conversion.


METHODS
AI, AII or angiotensin (1-7) were used in monovascular or bivascular perfusions.


RESULTS
The maximum gain in portal pressure induced by AII took place significantly earlier (P = 0.031) than that occurring after an equimolar AI infusion. The AI-induced PHR was abolished both by captopril or losartan, whereas the AII-induced PHR was not affected by captopril, but was abolished by losartan. Angiotensin (1-7) has no hemodynamic effect in the perfused liver. After partial hepatectomy, the AII-PHR pattern changes from a rapid return to baseline values to a pattern where there was no return to baseline values (3-7 days ex-surgery). In the bivascular perfusion system when AII was infused in the arterial branch in the retrograde mode of perfusion (peptide available only to the periportal zone), the PHR was at least 50% of that obtained when the prograde mode was used (peptide available to the periportal and perivenous zones).


CONCLUSIONS
AI does not induce PHR; this effect is a result of its mandatory conversion into AII by the ACE and the sequential action of AII on the AII receptor type 1 located in the hepatic periportal zone. AII induced PHR pattern changes during liver regeneration.
Carvalho
Leda Teixeira
LT
Department of Biochemistry, Federal University of São Paulo, São Paulo, Brazil.
Nascimento
Ecio Alves
EA
Teixeira
Felipe Oliveira
FO
Nagaoka
Márcia Regina
MR
Borges
Durval Rosa
DR
Kouyoumdjian
Maria
M
D000803:Angiotensin I / Q000378:metabolism*; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D004195:Disease Models, Animal; D006975:Hypertension, Portal / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D008102:Liver Circulation; D008115:Liver Regeneration / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D000959:Antihypertensive Agents; D000804:Angiotensin II; D000803:Angiotensin I