The present study was performed to evaluate the role of intrapulmonary activity of the two axes of the renin-angiotensin system (RAS): vasoconstrictor angiotensin-converting enzyme (ACE)/angiotensin II (ANG II)/ANG II type 1 receptor (AT1) axis, and vasodilator ACE type 2 (ACE2)/angiotensin 1-7 (ANG 1-7)/Mas receptor axis, in the development of hypoxic pulmonary hypertension in Ren-2 transgenic rats (TGR). Transgene-negative Hannover Sprague-Dawley (HanSD) rats served as controls. Both TGR and HanSD rats responded to two weeks´ exposure to hypoxia with a significant increase in mean pulmonary arterial pressure (MPAP), however, the increase was much less pronounced in the former. The attenuation of hypoxic pulmonary hypertension in TGR as compared to HanSD rats was associated with inhibition of ACE gene expression and activity, inhibition of AT1 receptor gene expression and suppression of ANG II levels in lung tissue. Simultaneously, there was an increase in lung ACE2 gene expression and activity and, in particular, ANG 1-7 concentrations and Mas receptor gene expression. We propose that a combination of suppression of ACE/ANG II/AT1 receptor axis and activation of ACE2/ANG 1-7/Mas receptor axis of the RAS in the lung tissue is the main mechanism explaining attenuation of hypoxic pulmonary hypertension in TGR as compared with HanSD rats.

<b><i>Objective:</i></b> We examined if renal denervation (RDN) attenuates the progression of aortocaval fistula (ACF)-induced heart failure or improves renal hemodynamics in Ren-2 transgenic rats (TGR), a model of angiotensin II (ANG II)-dependent hypertension. <b><i>Methods:</i></b> Bilateral RDN was performed 1 week after creation of ACF. The animals studied were ACF TGR and sham-operated controls, and both groups were subjected to RDN or sham denervation. In separate groups, renal artery blood flow (RBF) responses were determined to intrarenal ANG II (2 and 8 ng), norepinephrine (NE) (20 and 40 ng) and acetylcholine (Ach) (10 and 40 ng) 3 weeks after ACF creation. <b><i>Results:</i></b> In nondenervated ACF TGR, the final survival rate was 10 versus 50% in RDN rats. RBF was significantly lower in ACF TGR than in sham-operated TGR (6.2 ± 0.3 vs. 9.7 ± 0.5 mL min⁻¹ g⁻¹, <i>p</i> &#x3c; 0.05), the levels unaffected by RDN. Both doses of ANG II decreased RBF more in ACF TGR than in sham-operated TGR (−19 ± 3 vs. −9 ± 2% and −47 ± 3 vs. −22 ± 2%, <i>p</i> &#x3c; 0.05 in both cases). RDN did not alter RBF responses to the lower dose, but increased it to the higher dose of ANG II in sham-operated as well as in ACF TGR. NE comparably decreased RBF in ACF TGR and sham-operated TGR, and RDN increased RBF responsiveness. Intrarenal Ach increased RBF significantly more in ACF TGR than in sham-operated TGR (29 ± 3 vs. 17 ± 3%, <i>p</i> &#x3c; 0.05), the changes unaffected by RDN. ACF creation induced marked bilateral cardiac hypertrophy and lung congestion, both attenuated by RDN. In sham-operated but not in ACF TGR, RDN significantly decreased mean arterial pressure. <b><i>Conclusion:</i></b> The results show that RDN significantly improved survival rate in ACF TGR; however, this beneficial effect was not associated with improvement of reduced RBF or with attenuation of exaggerated renal vascular responsiveness to ANG II.

Recent studies have shown that long-term antihypertensive action of soluble epoxide hydrolase inhibition (sEHi) in angiotensin II (ANG II)-dependent hypertension might be mediated by the suppression of intrarenal ANG II levels. To test this hypothesis, we examined the effects of acute (2 days) and chronic (14 days) sEH inhibition on blood pressure (BP) in transgenic rats with inducible ANG II-dependent hypertension. ANG II-dependent malignant hypertension was induced by 10 days’ dietary administration of indole-3-carbinol (I3C), a natural xenobiotic that activates the mouse renin gene in Cyp1a1-Ren-2 transgenic rats. BP was monitored by radiotelemetry. Acute and chronic sEH inhibition was achieved using cis-4-[4-(3-adamantan-1-yl-ureido)cyclohexyloxy]benzoic acid (c-AUCB), given at doses of 0.3, 3, 13, 26, 60 and 130 mg/L in drinking water. At the end of experiments renal concentrations of epoxyeicosatrienoic acids (EETs), their inactive metabolites dihydroxyeicosatrienoic acids (DHETEs), and ANG II were measured. Acute BP-lowering effects of sEH inhibition in I3C-induced rats was associated with a marked increase in renal EETs/DHETEs ratio and acute natriuresis. Chronic treatment with c-AUCB in I3C-induced rats elicited dose-dependent persistent BP-lowering associated with a significant reduction of plasma and kidney ANG II levels. Our findings show that acute BP-lowering effect of sEH inhibition in I3C-induced Cyp1a1-Ren-2 transgenic rats is mediated by a substantial increase in intrarenal EETs and their natriuretic action without altering intrarenal RAS activity. Long-term antihypertensive action of c-AUCB in I3C-induced Cyp1a1-Ren-2 transgenic rats is mediated mostly by suppression of intrarenal ANG II concentration.

Objective We evaluated the therapeutic effectiveness of a new, orally active epoxyeicosatrienoic acid analog (EET-A) in rats with angiotensin II (ANG II)-dependent malignant hypertension. Methods Malignant hypertension was induced in Cyp1a1-Ren-2 transgenic rats by activation of the renin gene using indole-3-carbinol (I3C), a natural xenobiotic. EET-A treatment was started either simultaneously with I3C induction process (early treatment) or 10 days later during established hypertension (late treatment). Blood pressure (BP) (radiotelemetry), indices of renal and cardiac injury, and plasma and kidney levels of the components of the renin–angiotensin system (RAS) were determined. Results In I3C-induced hypertensive rats, early EET-A treatment attenuated BP increase (to 175 ± 3 versus 193 ± 4 mmHg, P < 0.05, on day 13), reduced albuminuria (15 ± 1 versus 28 ± 2 mg/24 h, P < 0.05), and cardiac hypertrophy as compared with untreated I3C-induced rats. This was associated with suppression of plasma and kidney ANG II levels (48 ± 6 versus 106 ± 9 and 122 ± 19 versus 346 ± 11 fmol/ml− or g, respectively, P < 0.05) and increases in plasma and kidney angiotensin (1–7) concentrations (84 ± 9 versus 37 ± 6 and 199 ± 12 versus 68 ± 9 fmol/ml or g, respectively, P < 0.05). Remarkably, late EET-A treatment did not lower BP or improve renal and cardiac injury; indices of RAS activity were not affected. Conclusion The new, orally active EET-A attenuated the development of experimental ANG II-dependent malignant hypertension, likely via suppression of the hypertensiogenic axis and augmentation of the vasodilatory/natriuretic axis of RAS.