title: Zonal heterogeneity in action of angiotensin-converting enzyme inhibitor on renal microcirculation: role of intrarenal bradykinin.
abstract: The present study examined the role of intrarenal bradykinin in angiotensin-converting enzyme inhibitor (ACEI)-induced dilation of renal afferent (AFF) and efferent arterioles (EFF) in vivo, and further evaluated whether ACEI-stimulated bradykinin activity differed in superficial (SP) and juxtamedullary nephrons (JM). Arterioles of canine kidneys were visualized with an intravital charge-coupled device camera microscope. E4177 (an angiotensin receptor antagonist, 30 microg/kg) dilated AFF and EFF in SP (15 +/- 3% and 19 +/- 5%) and JM (15 +/- 3% and 18 +/- 4%). Subsequently, cilazaprilat (30 microg/kg) caused further dilation of both AFF (29 +/- 4%) and EFF (36 +/- 4%) in JM, whereas in SP it dilated only EFF (29 +/-3%). Similarly, in the presence of E4177, cilazaprilat caused further increases in sodium excretion. This cilazaprilat-induced vasodilation and natriuresis was abolished by a bradykinin antagonist (N(alpha)-adamantaneacetyl-D-Arg-[Hyp3,Thi5,8,D-Phe7]b radykinin). In parallel with these results, cilazaprilat increased renal bradykinin content, more greatly in the medulla than in the cortex (5.7 +/- 0.4 versus 4.6 +/- 0.1 ng/g). Similarly, cilazaprilat elicited greater bradykinin-dependent increases of nitrite/nitrate in the medulla. In conclusion, zonal heterogeneity in renal bradykinin/nitric oxide levels and segmental differences in reactivity to bradykinin contribute to the diverse responsiveness of renal AFF and EFF to ACEI. ACEI-enhanced kinin action would participate in the amelioration of glomerular hemodynamics and renal sodium excretion by ACEI.
authors.affiliation: Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Matsuda
authors.forename: K
authors.initials: K
authors.lastname: Hayashi
authors.forename: K
authors.initials: K
authors.lastname: Arakawa
authors.forename: M
authors.initials: M
authors.lastname: Naitoh
authors.forename: E
authors.initials: E
authors.lastname: Kubota
authors.forename: M
authors.initials: M
authors.lastname: Honda
authors.forename: A
authors.initials: A
authors.lastname: Matsumoto
authors.forename: H
authors.initials: H
authors.lastname: Suzuki
authors.forename: T
authors.initials: T
authors.lastname: Yamamoto
authors.forename: F
authors.initials: F
authors.lastname: Kajiya
authors.forename: T
authors.initials: T
authors.lastname: Saruta
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D001920:Bradykinin / Q000502:physiology*; D017315:Cilazapril / Q000031:analogs & derivatives / Q000494:pharmacology; D004285:Dogs; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D008833:Microcirculation / Q000187:drug effects; D009569:Nitric Oxide / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D011945:Receptors, Angiotensin / Q000502:physiology; D012079:Renal Circulation / Q000187:drug effects*; D014664:Vasodilation / Q000187:drug effects
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D007093:Imidazoles; D011725:Pyridines; D011945:Receptors, Angiotensin; C083778:3-((2'-carboxybiphenyl-4-yl)methyl)-2-cyclopropyl-7-methyl-3H-imidazo(4,5-b)pyridine; D017315:Cilazapril; D009569:Nitric Oxide; D001920:Bradykinin; C045980:cilazaprilat