A pharmacological differentiation between postjunctional (AT1A) and prejunctional (AT1B) angiotensin II receptors in the rabbit aorta

Molecular mechanisms of vasoconstrictor action of imidazo[1,2-alpha]benzimidazole derivative RU-1117 possessing local anesthetic properties

We studied the mechanisms of action of imidazobenzimidazole derivative RU-1117 on calcium homeostasis in myocytes isolated from rat thoracic aorta. In therapeutic concentrations, RU-1117 increased the content of free calcium ions due to their mobilization from intracellular depot via the IP3-dependent mechanisms. Antagonists of angiotensin II AT1-receptors irbesartan and, to greater extent, eprosartan abolished the calcium-mobilizing action of RU-1117. Selective antagonist of endothelin ETA-receptors sitaxsentan and alpha1-adrenoceptor agonist prazosin produced no effect on calcium mobilization caused by novel local anesthetic RU-1117.

Introduction: The pharmacological profile of eprosartan--implications for cerebrovascular and cardiovascular risk reduction

Moderate elevations in blood pressure translate to significant increases in cardiovascular and cerebro vascular risk. Beneficially, this relationship allows small decreases in blood pressure to be associated with risk reduction. Both the renin-angiotensin system and the sympathetic nervous system are involved in hypertension, hence targeting these systems is likely to be of benefit in the treatment of hypertension. Angiotensin II type 1 receptor blockers (ARBs) are used for controlling blood pressure and treating heart failure in a broad range of patients, including those with diabetes and the elderly. Not only have ARBs shown good efficacy and tolerability, they also appear to have a protective effect that goes beyond that expected from the reduction of blood pressure. The ARB eprosartan is a nonbiphenyl nontetrazole angiotensin II type 1 receptor (AT1) antagonist, which acts to decrease total peripheral resistance. Eprosartan acts at vascular AT1 receptors (postsynaptically) and at presynaptic AT1 receptors, where it inhibits noradrenaline release. In clinical studies, eprosartan has been shown to significantly reduce cardiovascular and cerebrovascular events, whilst avoiding the persistent cough that commonly occurs with the use of angiotensin-converting enzyme inhibitors. Eprosartan can also be differentiated from other ARBs due to its noradrenergic effects, which other ARBs used at therapeutic doses do not possess. Eprosartan, therefore, represents a useful therapeutic option in the management of patients with hypertension, including those with a history of stroke or with co-morbid type 2 diabetes mellitus.

Risk reduction by preventing stroke: need for blockade of angiotensin II and catecholamines?

Angiotensin (AT) II and noradrenaline play major roles in hypertension, stroke and coronary heart disease, which are themselves interlinked. Harmful effects of AT II are not blocked solely by angiotensin-converting enzyme inhibitors, as it is now evident that AT II is generated by other enzymes such as chymase. Angiotensin II also stimulates noradrenaline release modulated by presynaptic receptors on sympathetic nerves. Numerous studies have defined the action of the AT II type 1 receptor blocker (ARB) eprosartan as controlling noradrenergic and adrenergic effects, resulting from actions on the renin-angiotensin-aldosterone system and the sympathetic nervous system. Clinical studies have been carried out to assess the effects of ARBs on morbidity and mortality. The Valsartan Antihypertensive Long-term Use Evaluation (VALUE) trial compared the effects of valsartan and the calcium channel blocker (CCB) amlodipine in over 15,000 patients at high risk of a cardiac event. Results showed that blood pressure was reduced by both treatments and cardiac mortality/morbidity was similar in both groups. By contrast, the Morbidity and mortality after Stroke, Eprosartan compared with nitrendipine for Secondary prevention (MOSES) study (n = 1405) generated results which differed from the VALUE study, in that blood pressure was reduced by both eprosartan and nitrendipine, but eprosartan reduced all cardiovascular and cerebrovascular events to a greater extent than nitrendipine. It is also possible that any delayed clinical benefit of eprosartan could be due to reverse cardiac remodelling. Eprosartan, by blocking AT II receptors, reducing noradrenaline release and blocking catecholamine actions, may, therefore, provide greater protection against vascular events than CCBs or other ARBs.