| Abstrakt: |
Previous in vivo studies in cardiomyopathic hamsters suggested that the expression of vasopressin (AVP) V2mRNA 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 V2mRNA and aquaporin-2 (AQP2) mRNA in the inner medullary collecting duct (IMCD) of the male Wistar rat. The expression of AVP V2mRNA 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, 10−9and 10−7mol/L). Angiotensin II caused a significant increase in the AVP V2mRNA 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 V2mRNA expression, we incubated IMCD with10−7and 10−11M 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 V2mRNA was abolished. In the fourth group, we examined the effect of protein kinase C (PKC) inhibition on V2mRNA expression. The upregulation of V2mRNA 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 V2mRNA and AQP2 mRNA in the IMCD, respectively. Dibutryl cAMP stimulated an upregulation in the expression of V2mRNA and AQP2 mRNA, whereas phorbol esters suppressed the expression of V2mRNA. These results suggested that PKA stimulates and PKC suppresses the expression of V2mRNA in the IMCD of the kidney. Copyright 2003, Elsevier Science (USA). All rights reserved. |
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