title: Desensitization of endothelin-1 binding by vasopressin via a cAMP-mediated pathway in rat CCD.
abstract: In renal collecting ducts, endothelin-1 (ET-1) inhibits Na+ reabsorption and antagonizes the effects of arginine vasopressin (AVP). Whether AVP may affect ET-1 action in the collecting ducts that mainly express the ETB receptor subtype, however, remains unknown. Since ETB, but not ETA, possesses a consensus amino acid sequence for possible phosphorylation by protein kinase A (PKA), we hypothesized that AVP may influence ET-1 binding to the ETB receptor via PKA. In microdissected rat cortical collecting ducts, the specific ET-1 binding decreased by 35% (15.6 +/- 4.4 vs. 24.0 +/- 3.6 amol/mm in control) following 20-min preincubation with 10(-7) M AVP. This decrease in ET-1 binding was mimicked by 10(-5) M forskolin and by 10(-4) M dibutyryl (DB) adenosine 3',5'-cyclic monophosphate (cAMP), indicating that this heterologous desensitization may be caused by a cAMP-dependent mechanism. Moreover, N-(2([3-(4-bromophenyl)-2-propenyl]-amino]-ethyl)-5- isoquinolinesulfonamide (H-89) and the Rp diastereoisomer of cAMP, Rp-cAMPS, which are both PKA-specific inhibitors, eliminated AVP-induced ETB receptor desensitization. The reduction in ET-1 binding was characterized by a decrease in binding affinity [dissociation constant (Kd) = 4 vs. 2 nM in control] with no change in maximal binding capacity. In contrast, forskolin and DBcAMP had no effect on ET-1 binding in endothelium-denuded aortic strips, which mainly express ETA subtype. These results showed that AVP rapidly downregulates the ETB receptor by reducing Kd through a PKA-dependent pathway. Thus ET-1 and AVP may act in a mutually antagonizing manner in the renal collecting ducts.
authors.affiliation: First Department of Internal Medicine, University of Tokyo Faculty of Medicine, Japan.
authors.forename: F
authors.initials: F
authors.lastname: Takemoto
authors.forename: S
authors.initials: S
authors.lastname: Uchida
authors.forename: H
authors.initials: H
authors.lastname: Katagiri
authors.forename: Y
authors.initials: Y
authors.lastname: Oka
authors.forename: A
authors.initials: A
authors.lastname: Nakao
authors.forename: K
authors.initials: K
authors.lastname: Kurokawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D001665:Binding Sites / Q000235:genetics; D003994:Bucladesine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015536:Down-Regulation; D016232:Endothelins / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology; D007672:Kidney Cortex / Q000187:drug effects* / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000187:drug effects* / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017466:Receptors, Endothelin / Q000235:genetics / Q000378:metabolism; D013237:Stereoisomerism; D013449:Sulfonamides
chemical_list: D016232:Endothelins; D007546:Isoquinolines; D017466:Receptors, Endothelin; D013449:Sulfonamides; D001127:Arginine Vasopressin; D005576:Colforsin; D003994:Bucladesine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide