Metabolism - Clinical and Experimental
Volume 52, Issue 3 , Pages 290-295, March 2003

Angiotensin II upregulates the expression of vasopressin V2 mRNA in the inner medullary collecting duct of the rat☆☆☆

Department of Medicine, University of British Columbia, Vancouver Hospital and Health Sciences Center, Vancouver, BC, Canada

Received 28 February 2002; accepted 16 September 2002.

Abstract 

Previous in vivo studies in cardiomyopathic hamsters suggested that the expression of vasopressin (AVP) V2 mRNA is up- regulated by angiotensin II. The present study was performed to determine whether angiotensin II plays a role in regulating the expression of AVP V2 mRNA and aquaporin-2 (AQP2) mRNA in the inner medullary collecting duct (IMCD) of the male Wistar rat. The expression of AVP V2 mRNA and AQP2 mRNA in the IMCD was measured by competitive reverse-transcriptase polymerase chain reaction (RT-PCR). Six groups of experiments were performed. In the first group, we incubated IMCD with 3 different doses of angiotensin II (10−11, 10−9 and 10−7 mol/L). Angiotensin II caused a significant increase in the AVP V2 mRNA in a dose-dependent manner but its effect on AQP2 mRNA was modest. This effect of angiotensin II was inhibited by angiotensin II receptor antagonist, [Sar1,Ile8]-angiotensin II. To examine the role of PKA in mediating an increase in AVP V2 mRNA expression, we incubated IMCD with10−7 and 10−11 M of angiotensin II in the presence of a specific protein kinase A (PKA) inhibitor, Rp diasteroisomer of adenosine 3'-5'-cylic monophosphothionate (Rp-cAMPS). The angiotensin II–induced upregulation of V2 mRNA was abolished. In the fourth group, we examined the effect of protein kinase C (PKC) inhibition on V2 mRNA expression. The upregulation of V2 mRNA induced by angiotensin II was greatly exaggerated when IMCD was incubated with angiotensin II and RO-31-8220 (PKC inhibitor). In the fifth and sixth groups of studies, we determined the direct effect of PKA and PKC on regulating the expression of V2 mRNA and AQP2 mRNA in the IMCD, respectively. Dibutryl cAMP stimulated an upregulation in the expression of V2 mRNA and AQP2 mRNA, whereas phorbol esters suppressed the expression of V2 mRNA. These results suggested that PKA stimulates and PKC suppresses the expression of V2 mRNA in the IMCD of the kidney. Copyright 2003, Elsevier Science (USA). All rights reserved.

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☆ Supported by a grant from the Heart and Stroke Foundation of BC & Yukon (N.L.M.W.).

☆☆ Address reprint requests to Norman L.M. Wong, PhD, Department of Medicine, Vancouver Hospital and Health Sciences Center, Koerner Pavilion, 2211 Wesbrook Mall, Vancouver, BC, Canada.

PII: S0026-0495(02)05263-0

doi:10.1053/meta.2003.50047

Metabolism - Clinical and Experimental
Volume 52, Issue 3 , Pages 290-295, March 2003

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