Intrarenal alterations of the angiotensin‐converting enzyme type 2/angiotensin 1–7 complex of the renin‐angiotensin system do not alter the course of malignant hypertension in Cyp1a1‐Ren‐2 transgenic rats

Abstract

The role of the intrarenal renin-angiotensin system (RAS) in the pathophysiology of malignant hypertension is not fully understood. Accumulating evidence indicates that the recently discovered vasodilator axis of the RAS, angiotensin-converting enzyme (ACE) type 2 (ACE2)/angiotensin 1-7 (ANG 1-7), constitutes an endogenous system counterbalancing the hypertensiogenic axis, ACE/angiotensin II (ANG II)/AT1 receptor. This study aimed to evaluate the role of the intrarenal vasodilator RAS axis in the pathophysiology of ANG II-dependent malignant hypertension in Cyp1a1-Ren-2 transgenic rats. ANG II-dependent malignant hypertension was induced by 13 days' dietary administration of indole-3-carbinol (I3C), a natural xenobiotic that activates the mouse renin gene in Cyp1a1-Ren-2 transgenic rats. It was hypothesized that pharmacologically-induced inhibition of the ACE2/ANG 1-7 complex should aggravate, and activation of this axis should attenuate, the course of ANG II-dependent malignant hypertension. Blood pressure (BP) was monitored by radiotelemetry. ACE2 inhibitor (DX 600, 0.2 μg/day) and ACE2 activator (DIZE, 1 mg/day) were administrated via osmotic minipumps. Even though ACE2 inhibitor significantly decreased and ACE2 activator increased intrarenal ANG 1-7 concentrations, the course of BP, as well as of albuminuria, cardiac hypertrophy and renal glomerular damage, were not altered. It was shown that intrarenal alterations in the ACE2/ANG 1-7 complex did not significantly modify the course of malignant hypertension in I3C-induced Cyp1a1-Ren-2 transgenic rats. Thus, in our experimental setting alterations of this intrarenal vasodilator complex of the RAS do not significantly modify the form of malignant hypertension that clearly depends on the inappropriately increased activity of the ACE/ANG II/AT1 receptor axis.

Epoxyeicosatrienoic acid analog attenuates the development of malignant hypertension, but does not reverse it once established

“…In this protocol, one unit of angiotensin-converting enzyme (ACE) activity was defined as the amount of enzyme required to release 1 μmol of hippuric acid/minute/liter of serum at 37 °C. In this study, ACE activity was also estimated as the ANG II to ANG I ratio, because we have recently found that in this ANG II-dependent model of hypertension, in accordance with one original study in ANG II-infused hypertensive rats, the ratio is a very reliable index for assessment of circulating and especially tissue ACE activity [47–50]. Plasma and kidney tissue renin, angiotensin-converting enzyme type 2 (ACE2) activities, and angiotensin-(1–7) (ANG 1–7) levels were measured as described previously [47–50].…”

“…In this study, ACE activity was also estimated as the ANG II to ANG I ratio, because we have recently found that in this ANG II-dependent model of hypertension, in accordance with one original study in ANG II-infused hypertensive rats, the ratio is a very reliable index for assessment of circulating and especially tissue ACE activity [47–50]. Plasma and kidney tissue renin, angiotensin-converting enzyme type 2 (ACE2) activities, and angiotensin-(1–7) (ANG 1–7) levels were measured as described previously [47–50]. In addition, expression of liver Ren-2 renin gene, of ANG II type 1 (AT 1 ) receptor and G-protein-coupled receptor Mas gene (as a functional receptor for ANG 1–7) in the kidney, and of ACE and ACE2 gene in the kidney were determined as detailed previously [48–50].…”

“…Plasma and kidney tissue renin, angiotensin-converting enzyme type 2 (ACE2) activities, and angiotensin-(1–7) (ANG 1–7) levels were measured as described previously [47–50]. In addition, expression of liver Ren-2 renin gene, of ANG II type 1 (AT 1 ) receptor and G-protein-coupled receptor Mas gene (as a functional receptor for ANG 1–7) in the kidney, and of ACE and ACE2 gene in the kidney were determined as detailed previously [48–50]. The levels of the arachidonic acid metabolites, EETs, and DHETEs were measured in the kidney cortex.…”

“…The levels of the arachidonic acid metabolites, EETs, and DHETEs were measured in the kidney cortex. Samples were extracted, separated by reverse-phase HPLC, and analyzed by negative-mode electrospray ionization and tandem mass spectroscopy as described previously [47–50]. The procedures for blood sampling, the assays of individual components of RAS, and the EET and DHETE assays are routinely employed in our laboratory, and this standardized approach allows us to compare the results with those of our previous studies evaluating the role of the RAS and CYP-dependent metabolites in the pathophysiology of ANG II-dependent form of hypertension [24,26,35].…”

The Role of Renal Vascular Reactivity in the Development of Renal Dysfunction in Compensated and Decompensated Congestive Heart Failure

“…The catecholamine concentrations were measured by a solid phase enzyme-linked immunosorbent assay (ELISA) based on the sandwich principle, using the commercially available ELISA kit (RE59395, IBL International, Hamburg, Germany). All methods are routinely employed in our laboratories [43,[45][46][47].…”