title: Endothelin upregulates the expression of vasopressin V2 mRNA in the inner medullary collecting duct of the rat.
abstract: Recent studies in our laboratory have demonstrated that bosentan, a mixed endothelin ET(A)/ET(B) receptor antagonist, prevented the upregulation of the arginine vasopressin (AVP) V(2) receptor in the inner medullary collecting duct (IMCD) of cardiomyopathic hamsters. These results suggested that endothelin-1 (ET-1) is involved in the upregulation of AVP V(2) receptors. Studies were performed to detect the effect of ET-1 on the expression of AVP V(2) receptors and the ET receptor mediating these effects within the IMCD of the rat. Rat IMCD tissue was isolated and incubated with the following: ET-1, or ET-1 in combination with ET(A) and ET(B) receptor antagonists BQ-123 and BQ-788, respectively, and sarafotoxin c (S6c), an ET(B) receptor-specific agonist. Tissue samples were then analyzed using quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) and Western blotting. ET-1 treatment resulted in increased V(2) mRNA from a control level of 186.8 +/- 15.0 amol/microg total RNA to 430.7 +/- 49.0 amol/microg total RNA (P <.003). ET-1/ET(A) treatment resulted in no significant decrease in V(2) mRNA expression 335.0 +/- 38.0 amol/microg total RNA. Whereas ET-1/ET(B), and ET-1/ET(B)/ET(A) treatment resulted in V(2) mRNA approaching control 256.0 +/- 15.0 amol/microg total RNA, and 215.6 +/- 42.3 amol/microg total RNA. However, ET-3 treatment produced no significant changes in V(2) receptor mRNA expression. Sarafotoxin treatment corroborated both the ET-1 and ET receptor antagonist data, demonstrating striking significant increases in V(2) receptor mRNA and protein expression. S6c treatment increased V(2) mRNA expression from a control level of 199 +/- 17.3 amol/microg total RNA to 284.3 +/- 42.1 amol/microg total RNA (P < 05). Western blotting revealed that changes in V(2) mRNA expression in the various treatment conditions were similar to changes in protein expression. Overall, these data indicate that in the IMCD ET-1 increases AVP V(2) receptor expression and these changes are mediated by the ET(B) receptor.
authors.affiliation: University of British Columbia, Vancouver Hospital and Health Sciences Center, Vancouver, Canada.
authors.forename: Marc
authors.initials: M
authors.lastname: Sonntag
authors.forename: Min Hui
authors.initials: MH
authors.lastname: Wang
authors.forename: Min Ho
authors.initials: MH
authors.lastname: Huang
authors.forename: Norman L M
authors.initials: NL
authors.lastname: Wong
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004305:Dose-Response Relationship, Drug; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D019334:Endothelin-3 / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D017483:Receptors, Vasopressin / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D015854:Up-Regulation / Q000187:drug effects; D014757:Viper Venoms / Q000494:pharmacology
chemical_list: D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D019334:Endothelin-3; D012333:RNA, Messenger; D017483:Receptors, Vasopressin; D014757:Viper Venoms; C057354:sarafotoxins s6