Angiotensin II synthesis

A parallel system for angiotensin generation exists in several other tissues (eg, heart) and may be responsible for trophic changes such as cardiac hypertrophy. The converting enzyme involved in tissue angiotensin II synthesis is also inhibited by ACE inhibitors. 

The Paal-Knorr furan synthesis can also be used to prepare 2,5-arylalkylfurans, as illustrated in the following example. Salimbeni produced furan 29 from dione 28 and subsequently used the furan as an intermediate for the production of angiotensin II receptor antagonists. ... 

Give an mRNA sequence that will code for the synthesis of angiotensin II. 

Endothelial cells are the major source of ET-1-synthesis. ET-1 is also produced by astrocytes, neurons, hepatocytes, bronchial epithelial cells, renal epithelial and mesangial cells. Physiological stimuli of ET-1-synthesis in endothelial cells are angiotensin II, catecholamines, thrombin, growth factors, insulin, hypoxia and shear stress. Inhibitors of ET-1 synthesis are atrial natriuretic peptide, prostaglandin E2 and prostacyclin. ET-2 is mainly synthesized in kidney, intestine, myocardium and placenta and ET-3 is predominantely produced by neurons, astrocytes and renal epithelial cells. 

The kidney contains the major site of renin synthesis, the juxtaglomerular cells in the wall of the afferent arteriole. From these cells, renin is secreted not only into the circulation but also into the renal interstitium. Moreover, the enzyme is produced albeit in low amounts by proximal tubular cells. These cells also synthesize angiotensinogen and ACE. The RAS proteins interact in the renal interstitium and in the proximal tubular lumen to synthesize angiotensin II. In the proximal tubule, angiotensin II activates the sodium/hydrogen exchanger (NHE) that increases sodium reabsorption. Aldosterone elicits the same effect in the distal tubule by activating epithelial sodium channels (ENaC) and the sodium-potassium-ATPase. Thereby, it also induces water reabsotption and potassium secretion. 

In the interstitium, angiotensin II induces proliferation of mesangial cells and fibroblasts and the synthesis of collagen and other matrix molecules by these cells via the ATI receptor. Moreover, by the concomitant stimulation of chemoattractant cytokines, inflammation is induced. These processes are mediated by endothelin, transforming growth factor(3, and reactive oxygen species, and finally lead to interstitial fibrosis and glomerulosclerosis observed in hypertension and diabetes. 

In 2004, Alterman et al. used a microwave-assisted Ullmann-type protocol for the synthesis of N-(f-butyl)-3-[4-(lH-imidazol-l-yl)benzyl]-5-isobutylthiophene-2-sulfonamide (Scheme 106) [61]. Deprotection of the sulfonamide followed by carbamate formation via reaction with butyl chloro-formate finally gave the target compound for biological evaluation as selective angiotensin II AT2 receptor agonist. The IH-imidazole derivative, however, showed only a low affinity for the AT2 receptor (Ki value > 10 p,M). 

Murugesan N, Gu Z, Fadnis L, et al. Dual angiotensin II and endothelin A receptor antagonists synthesis of 2 -substituted N-3-isoxazolyl biphenylsulfonamides with improved potency and pharmacokinetics. J Med Chem 2005 48 171-179. 

The same group of authors has recently reported a combination of various palladium- and copper-catalyzed Suzuki, cyanation, and Ullmann condensation reactions for the synthesis of thiophene-based selective angiotensin II AT2 receptor antagonists (Scheme 6.24) [55],... 

A deficiency in the local synthesis of vasodilating substances in the vascular endothelium, such as prostacyclin, bradykinin, and nitric oxide, or an increase in production of vasoconstricting substances such as angiotensin II and endothelin I ... 

I to angiotensin II, a potent vasoconstrictor and stimulator of aldosterone secretion. ACE inhibitors also block the degradation of bradykinin and stimulate the synthesis of other vasodilating substances including prostaglandin E2 and prostacyclin. The fact that ACE inhibitors lower BP in patients with normal plasma renin activity suggests that bradykinin and perhaps tissue production of ACE are important in hypertension. 

Competitive blocker of a-adrenergic receptors in heart and blood vessels Inhibits the enzyme HMG-CoA reductase and reduces the biosynthesis of cholesterol Acts as an angiotensin II receptor antagonist Inhibits the synthesis of prostaglandins via the selective inhibition of the enzyme cyclooxygenase-2... 

Figure 22.15 How angiotensin-II increases blood pressure. Angiotensin-II causes vasoconstriction of smooth muscle in arterioles in addition, it stimulates synthesis and hence secretion of aldosterone from the adrenal cortex. Both of these effects increase blood pressure.

Kiyama, R., Honma, T., Hayashi, K., Ogawa, M., Hara, M., Fujimoto, M., and Fujishita, T. Angiotensin II receptor antagonists. Design, synthesis, and in vitro evaluation of dibenzo[a,d]cycloheptene and dibenzo[b,f oxepin derivatives. 

High levels of circulating angiotensin II will stimulate the AT2-receptor and this mechanism may counteract the noxious process of vascular and myocardial remodeling. A potential theoretical advantage of the AT-receptor blockers over the ACE-inhibitors may be the inhibition of all Ang II effects at the AT-receptor level. ACE-inhibitors suppress a major portion of the Ang II synthesis, but the... 

Angiotensin II stimulates aldosterone synthesis and secretion from the glomerulosa cells of the adrenal cortex. The aldosterone secretion induced by angiotensin II in humans is not accompanied by an increase in glucocorticoid plasma levels. Chronic administration of angiotensin II will maintain elevated aldosterone secretion for several days to weeks unless hypokalemia ensues. 

In addition, a new class of drugs, termed vasopepti-dase inhibitors, inhibit the enzymatic activity of ACE and neutral endopeptidase, the enzyme responsible for the breakdown of natriuretic peptides. The end result is a reduction in the synthesis of angiotensin II and an increase in the circulating level of natriuretic peptides such as ANP. Omapatrilat, a vasopeptidase inhibitor, is under study for the treatment of hypertension and congestive heart failure. 

A. Angiotensin II has diverse physiological effects, including stimulating the synthesis and release of aldosterone from the adrenal cortex. This effect of angiotensin II results in fluid and water retention. The other answers are incorrect in that angiotensin II... 

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