Selective angiotensin-converting enzyme C-domain inhibition is sufficient to prevent angiotensin I-induced vasoconstriction.
Somatic angiotensin-converting enzyme (ACE) contains 2 domains (C-domain and N-domain) capable of hydrolyzing angiotensin I (Ang I) and bradykinin. Here we investigated the effect of the selective C-domain and N-domain inhibitors RXPA380 and RXP407 on Ang I-induced vasoconstriction of porcine femoral arteries (PFAs) and bradykinin-induced vasodilation of preconstricted porcine coronary microarteries (PCMAs). Ang I concentration-dependently constricted PFAs. RXPA380, at concentrations >1 mumol/L, shifted the Ang I concentration-response curve (CRC) 10-fold to the right. This was comparable to the maximal shift observed with the ACE inhibitors (ACEi) quinaprilat and captopril. RXP407 did not affect Ang I at concentrations < or =0.1 mmol/L. Bradykinin concentration-dependently relaxed PCMAs. RXPA380 (10 micromol/L) and RXP407 (0.1 mmol/L) potentiated bradykinin, both inducing a leftward shift of the bradykinin CRC that equaled approximately 50% of the maximal shift observed with quinaprilat. Ang I added to blood plasma disappeared with a half life (t(1/2)) of 42+/-3 minutes. Quinaprilat increased the t(1/2) approximately 4-fold, indicating that 71+/-6% of Ang I metabolism was attributable to ACE. RXPA380 (10 micromol/L) and RXP407 (0.1 mmol/L) increased the t(1/2) approximately 2-fold, thereby suggesting that both domains contribute to conversion in plasma. In conclusion, tissue Ang I-II conversion depends exclusively on the ACE C-domain, whereas both domains contribute to conversion by soluble ACE and to bradykinin degradation at tissue sites. Because tissue ACE (and not plasma ACE) determines the hypertensive effects of Ang I, these data not only explain why N-domain inhibition does not affect Ang I-induced vasoconstriction in vivo but also why ACEi exert blood pressure-independent effects at low (C-domain-blocking) doses.
van Esch
Joep H M
JH
Department of Pharmacology, Erasmus MC, Rotterdam, The Netherlands.
Tom
Beril
B
Dive
Vincent
V
Batenburg
Wendy W
WW
Georgiadis
Dimitris
D
Yiotakis
Athanasios
A
van Gool
Jeanette M G
JM
de Bruijn
René J A
RJ
de Vries
René
R
Danser
A H Jan
AH
D000293:Adolescent; D000328:Adult; D000803:Angiotensin I / Q000378:metabolism*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D001920:Bradykinin / Q000378:metabolism* / Q000494:pharmacology; D002216:Captopril / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005263:Femoral Artery / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000187:drug effects; D008875:Middle Aged; D009842:Oligopeptides / Q000494:pharmacology; D009928:Organ Specificity; D007703:Peptidyl-Dipeptidase A / Q000097:blood / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D010721:Phosphinic Acids / Q000494:pharmacology; D017434:Protein Structure, Tertiary / Q000187:drug effects; D012995:Solubility; D013329:Structure-Activity Relationship; D034421:Sus scrofa; D044005:Tetrahydroisoquinolines / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects* / Q000502:physiology
D000806:Angiotensin-Converting Enzyme Inhibitors; D009842:Oligopeptides; D010721:Phosphinic Acids; C118733:RXP 407; C476531:RXPA380; D044005:Tetrahydroisoquinolines; C054501:quinaprilat; D000803:Angiotensin I; D002216:Captopril; D007703:Peptidyl-Dipeptidase A; D001920:Bradykinin