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

Previous in vivo studies in cardiomyopathic hamsters suggested that the expression of vasopressin (AVP) V-2 mRNA is upregulated by angiotensin 11. The present study was performed to determine whether angiotensin II plays a role in regulating the expression of AVP V-2 mRNA and aquaporin-2 (AQP2) mRNA in the inner medullary collecting duct (IMCD) of the male Wistar rat. The expression of AVP V-2 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 V-2 mRNA in a dose-dependent manner but its effect on AQP2 mRNA was modest. This effect of angiotensin 11 was inhibited by angiotensin 11 receptor antagonist, [Sar(1),Ile(8)]-angiotensin II. To examine the role of PKA in mediating an increase in AVP V-2 mRNA expression, we incubated IMCD with 10(-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 V-2 mRNA was abolished. In the fourth group, we examined the effect of protein kinase C (PKC) inhibition on V-2 mRNA expression. The upregulation of V-2 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 V-2 mRNA and AQP2 mRNA in the IMCD, respectively. Dibutryl cAMP stimulated an upregulation in the expression of V-2 mRNA and AQP2 mRNA, whereas phorbol esters suppressed the expression of V-2 mRNA. These results suggested that PKA stimulates and PKC suppresses the expression of V-2 mRNA in the IMCD of the kidney. Copyright 2003 Elsevier Science (USA). All rights reserved.