Enalapril and losartan augment endogenous nitric oxide release in Takayasu's arteritis--a case report

Renoprotection against complete unilateral ureteric obstruction: Is there an ultimate choice?

Objectives

To evaluate and compare the relative contribution of different therapeutic agents for renoprotection against complete unilateral ureteric obstruction (UUO), using a rabbit model sampled at different times.

Materials and methods

Eighty-four male New Zealand White rabbits were divided into seven groups of 12 rabbits; a sham group, a control (left UUO + no medication) or left UUO and treated with either enalapril, losartan, verapamil, l-arginine or antioxidant (vitamin E and selenium mixture). Rabbits in the control and treated groups were subjected to 3, 10 and 21 days of complete ureteric ligation and then killed humanely. The control and treated groups were evaluated at baseline and at the end of the experiment, by measuring split effective renal plasma flow (ERPF) using diuretic renography, and the split glomerular filtration rate (GFR) using selective creatinine clearance. Renal histopathology was evaluated using a tubulo-interstitial damage score.

Results

In the sham group there was no significant effect on any of the evaluated variables. For split ERPF, losartan showed the highest renoprotective effect, saving 44% and 77% of ERPF at 3 and 21 days after UUO, respectively. Losartan was also the best renoprotective agent for GFR. For renal histopathology, enalapril showed the earliest and greatest improvement as assessed by the damage score, reaching 60% at 21 days after UUO. l-Arginine was the next best effect to blockade the renin-angiotensin system for renoprotection.

Conclusion

We suggest that blockade of the renin-angiotensin system provides the best renoprotection against the effects of complete UUO.

Takayasu's arteritis

The frequency of Takayasu's arteritis (TA) has been estimated to be 2.9 cases per 1 million people, with a female preponderance, although female-to-male ratio varies from different geographic areas. A high frequency of haplotype A24-B52-DR2 has been found in Japanese patients, without this association in other populations. TA has a striking predilection for the aortic arch and its branches. Evidence favors an autoimmune pathogenesis. Segmental inflammation (active and inactive lesions) may coexist. Due to its enhanced resolution, magnetic resonance imaging and magnetic resonance angiography eventually will replace catheterization angiography. Mortality reduction with glucocorticoid treatment has not been firmly established.

Therapeutic potential of angiotensin II receptor antagonists

The circulating renin-angiotensin system plays an important role in cardiovascular homeostasis. More importantly, the local tissue renin angiotensin plays a pivotal role in cell growth and remodelling of cardiomyocytes and on the peripheral arterial vasculature. In addition, the renin angiotensin system is related to apoptosis, control of baroreflex and autonomic responses, vascular remodelling and regulation of coagulation, inflammation and oxidation. The cardioprotective and vascular protective effects of the angiotensin receptive blockade appears to be related to selective blockade of the angiotensin II (A-II) Type I (AT(1)) receptors. However, there is now growing evidence showing that some of the effects of AT-II receptor blockers (ARBs) are related to the activation of the kinin pathways. This paper will review some of the recent mechanisms related to the cardiovascular effects of angiotensin and more specifically of ARBs. This paper will present the novel data on the role of ARB in the development of atherosclerosis, vascular remodelling, coagulation balance and autonomic regulation. Finally, the role of ARBs, used alone or in combination with ACE inhibitor in patients with heart failure, will be discussed.