Angiotensinconverting Enzyme

Endothelial cells synthesize and express on their surface angiotensin-converting enzyme (ACE),102 the protein that converts angiotensin I to the potent vasoconstrictor angiotensin II and degrades and inactivates bradykinin. Of note, vascular cells contain almost all components of the renin/angiotensin system, and thus local production of angiotensin II can contribute importantly to vascular function. This local production of angiotensin II can explain why ACE inhibitors and angiotensin receptor antagonists are often effective even when the circulating levels of renin or angiotensin II are not elevated.

Endothelial Control of Vascular Growth

As with vascular tone, the endothelium also exerts a dual effect on vascular growth (Fig. 6-5). Both growth-promoting and growth-inhibitory factors are made and secreted by endothelial cells, making them pivotal in the control of smooth muscle responsiveness. Endothelial cells are involved in two types of vascular growth: angiogenesis and abnormal growth of smooth muscle during disease.

Figure 6-5: Endothelial control of vascular growth. As with vasoactive substances, endothelial cells make and secrete both growth-promoting (white boxes) and growth-inhibitory (colored boxes) compounds. Under normal conditions, the net effect of the endothelium is growth inhibitory. Abbreviations: EDRF = endothelial-derived relaxing factor; NO = nitric oxide; TGF-ß = transforming growth factor-ß; PDGF = platelet-derived growth factor; IGF-I = insulin-like growth factor-I; IL-1 = interleukin-1; FGF = fibroblast growth factor. (Courtesy of Bernard Lassègue, Ph.D.)

Figure 6-5: Endothelial control of vascular growth. As with vasoactive substances, endothelial cells make and secrete both growth-promoting (white boxes) and growth-inhibitory (colored boxes) compounds. Under normal conditions, the net effect of the endothelium is growth inhibitory. Abbreviations: EDRF = endothelial-derived relaxing factor; NO = nitric oxide; TGF-ß = transforming growth factor-ß; PDGF = platelet-derived growth factor; IGF-I = insulin-like growth factor-I; IL-1 = interleukin-1; FGF = fibroblast growth factor. (Courtesy of Bernard Lassègue, Ph.D.)

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Essentials of Human Physiology

Essentials of Human Physiology

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