title: Potentiation of the actions of bradykinin by angiotensin I-converting enzyme inhibitors. The role of expressed human bradykinin B2 receptors and angiotensin I-converting enzyme in CHO cells.
abstract: Part of the beneficial effects of angiotensin I-converting enzyme (ACE) inhibitors are due to augmenting the actions of bradykinin (BK). We studied this effect of enalaprilat on the binding of [3H]BK to Chinese hamster ovary (CHO) cells stably transfected to express the human BK B2 receptor alone (CHO-3B) or in combination with ACE (CHO-15AB). In CHO-15AB cells, enalaprilat (1 mumol/L) increased the total number of low-affinity [3H]BK binding sites on the cells at 37 degrees C, but not at 4 degrees C, from 18.4 +/- 4.3 to 40.3 +/- 11.9 fmol/10(6) cells (P < .05; Kd, 2.3 +/- 0.8 and 5.9 +/- 1.3 nmol/L; n = 4). Enalaprilat preserved a portion of the receptors in high-affinity conformation (Kd, 0.17 +/- 0.08 nmol/L; 8.1 +/- 0.9 fmol/10(6) cells). Enalaprilat decreased the IC50 of [Hyp3-Tyr(Me)8]BK, the BK analogue more resistant to ACE, from 3.2 +/- 0.8 to 0.41 +/- 0.16 nmol/L (P < .05, n = 3). The biphasic displacement curve of the binding of [3H]BK also suggested the presence of high-affinity BK binding sites. Enalaprilat (5 nmol to 1 mumol/L) potentiated the release of [3H]arachidonic acid and the liberation of inositol 1,4,5-trisphosphate (IP3) induced by BK and [Hyp3-Tyr(Me)8]BK. Moreover, enalaprilat (1 mumol/L) completely and immediately restored the response of the B2 receptor, desensitized by the agonist (1 mumol/L [Hyp3-Tyr(Me)8]BK); this effect was blocked by the antagonist, HOE 140. Finally, enalaprilat, but not the prodrug enalapril, decreased internalization of the receptor from 70 +/- 9% to 45 +/- 9% (P < .05, n = 7). In CHO-3B cells, enalaprilat was ineffective. ACE inhibitors in the presence of both the B2 receptor and ACE enhance BK binding, protect high-affinity receptors, block receptor desensitization, and decrease internalization, thereby potentiating BK beyond blocking its hydrolysis.
authors.affiliation: Department of Pharmacology, University of Illinois College of Medicine, Chicago, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Minshall
authors.forename: F
authors.initials: F
authors.lastname: Tan
authors.forename: F
authors.initials: F
authors.lastname: Nakamura
authors.forename: S F
authors.initials: SF
authors.lastname: Rabito
authors.forename: R P
authors.initials: RP
authors.lastname: Becker
authors.forename: B
authors.initials: B
authors.lastname: Marcic
authors.forename: E G
authors.initials: EG
authors.lastname: Erdös
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology* / Q000502:physiology; D016466:CHO Cells; D006224:Cricetinae; D018014:Gene Transfer Techniques; D006801:Humans; D007703:Peptidyl-Dipeptidase A / Q000502:physiology*; D018002:Receptors, Bradykinin / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D018002:Receptors, Bradykinin; D007703:Peptidyl-Dipeptidase A; D001920:Bradykinin