[3H]ramiprilat binding to the angiotensin-converting enzyme in rat renal brush-border membranes: the effect of chloride.
The [3H]ramiprilat binding to the angiotensin-converting enzyme (ACE) in rat renal brush-border membranes was studied. At pH 7.9, and in the presence of 50 mM NaCl, specific binding of [3H]ramiprilat was saturable with a dissociation constant KD = 5.05 nM and maximum number of binding sites of 1.52 pmol/mg prot. [3H]Ramiprilat binding was completely inhibited by specific inhibitors of ACE: ramiprilat, ramipril, enalaprilat, enalapril and captopril. [3H]Ramiprilat binding was Zn2(+)- and Cl(-)-dependent. In the presence of EGTA, which chelates Zn2+ ions, ramiprilat binding was inhibited, but the addition of Zn2+ restored the initial binding. Binding was maximum in the presence of 10 mM NaCl while higher NaCl concentrations decreased the binding, corresponding to a decrease in affinity. The association and dissociation kinetics were also NaCl-dependent. In the absence of NaCl, association and dissociation kinetics were rapid and monophasic. Two-step dissociation kinetics appeared in the presence of 10, 50 and 300 mM NaCl and dissociation time increased with the NaCl concentration. These results confirmed the role of Cl- in the isomerisation and the stability of the membrane-associated ACE-inhibitor complex.
Grima
M
M
Institut de Pharmacologie, URA DO589 CNRS, Université Louis Pasteur, Strasbourg, France.
Mosser
J
J
Welsch
C
C
Barthelmebs
M
M
Imbs
J L
JL
D000469:Alkaline Phosphatase / Q000378:metabolism; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002712:Chlorides / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000201:enzymology; D008871:Microvilli / Q000187:drug effects / Q000201:enzymology; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D011758:Pyrroles / Q000378:metabolism*; D011817:Rabbits; D017257:Ramipril / Q000031:analogs & derivatives*; D051381:Rats; D012965:Sodium Chloride / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology
D000806:Angiotensin-Converting Enzyme Inhibitors; D002712:Chlorides; D011758:Pyrroles; D012965:Sodium Chloride; D004533:Egtazic Acid; C052549:ramiprilat; D000469:Alkaline Phosphatase; D007703:Peptidyl-Dipeptidase A; D015032:Zinc; D017257:Ramipril