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Vasoactive peptides are autacoids with significant actions on vascular smooth muscle as well as other tissues. They include vasoconstrictors, vasodilators, and peptides with mixed effects. Antagonists of these peptides or the enzymes that produce them have useful clinical properties.

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In addition to their actions on smooth muscle, vasoactive peptides function as neurotransmitters and local and systemic hormones. The better-known vasoactive peptides include angiotensin, bradykinin, natriuretic peptides, calcitoningene-related peptide (CGRP), endothelin, neuropeptide Y (NPY), substance P and vasoactive intestinal peptide (VIP) (discussed in this chapter), and vasopressin (Chapters 15 and 37). Many other endogenous peptides with very important actions (eg, insulin, glucagon, opioid peptides) have less or no direct vascular smooth muscle effects.

Vasoactive peptides probably all act on cell surface receptors. Most act via G-protein-coupled receptors and cause the production of well-known second messengers (Table 17–1); a few may open ion channels.

Table 17–1 Some Vasoactive Peptides and Their Properties.
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KininsFamily of vasoactive peptides associated with tissue injury and inflammation, for example, bradykinin
Natriuretic peptidesFamily of peptides synthesized in brain, heart, and other tissues; have vasodilator as well as natriuretic effects
NeuropeptidesPeptides with prominent roles as neurotransmitters or modulators; many also have potent smooth muscle effects
PeptidaseFamily of enzymes that activate or inactivate peptides by hydrolysis, for example, angiotensin-converting enzyme (dipeptidyl peptidase), neutral endopeptidase
TachykininsGroup of 3 potent neuropeptides: substance P, neurokinin A, and neurokinin B

Source and Disposition

Angiotensin I is produced from circulating angiotensinogen by renin, an enzyme released ...

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