Vascular smooth muscle, regulation contraction

Smooth muscles do more than contract and the regulation of the mitotic activity of vascular smooth muscle is important in the maintenance of the oxygen supply to tissues and the genesis of hypertension of non-renal origin. Secretion activities of smooth muscle are just beginning to be appreciated. 

The regulation of smooth muscle contraction and relaxation is shown schematically in Figure 12-1. The mechanisms of action of the major types of vasodilators are listed in Table 11-2. As shown in Figures 12-1 and 12-2, drugs may relax vascular smooth muscle in... 

Vascular smooth muscle cells the cells that surround the blood vessels and control blood pressiue by relaxing or contracting in response to specific signals, including -NO Vascular tone the degree of contraction of the vascular smooth muscle cells that regulates blood pressure Vasodilation or vasodilatation expansion of the blood vessels as a result of relaxation of the smooth muscle cells that overlie the vessels, resulting in decreased blood pressure... 

Hrometz SL, Edelmann SE, McCune DF, et al. Expression of multiple a,-adrenoceptors on vascular smooth muscle correlation with the regulation of contraction. J Pharmacol Exp Ther 1999 290 452-463. 

Cyclic AMP (cAMP) is an important intracellular mediator regulating the activation of inflammatory cells. Particularly important with respect to asthma, cAMP also plays a role in regulating airway and vascular smooth muscle contractibility, inflammatory cell proliferation, and pulmonary neuronal responsiveness. Cyclic phosphodiesterases (PDEs) comprise a protein superfamily, whose function is to inactivate cyclic AMP and cyclic GMP. The fact that certain PDE inhibitors suppress immune cell functions in vitro and pulmonary inflammation in vivo may represent an opportunity for the development of novel anti-inflammatory drugs. 

Muscarinic acetylcholine receptors are present in the mammalian central nervous system (CNS) and in the periphery. Their stimulation produces inhibitory responses such as bradycardia and vascular smooth muscle dilatation, and excitatory responses such as ganglionic depolarization and smooth muscle contraction. Muscarinic receptors of the CNS are involved in motor control, temperature and sleep regulation, and in processes including higher cognitive functions such as memory and learning. 

The mechanism of cardiac contraction involves a G-protein signal transduction pathway, which regulates intracellular calcium concentrations. Activation of the Gs-protein involves the formation of intracellular cAMP, which thereby increases intracellular calcium, stimulating cardiac muscle contraction (see Chapter 4). Relaxation occurs when the released cAMP is hydrolyzed by cytosolic cAMP-dependent PDE3, one of the phosphodiesterase isofoms. Therefore, inhibition of PDE3 increases intracellular cAMP, promoting cardiac muscle contraction but vasodilation of vascular smooth muscle. (See Chapter 17 for more information about phosphodiesterases.)... 

Overview of the Regulation of Vascular Smooth Muscle Contraction and Relaxation (1)... 

The heart, as an endocrine organ itself, secretes the atrial natriuretic peptide, which has several important influences on the cardiovascular system. In addition to atrial natriuretic peptide, catecholamines, thyroid hormones, mineralocorticoids, sex steroids, and angiotensin II are other hormones also known to exert their effects on the cardiovascular functions and blood pressure. Hormones regulate the contraction and dilatation of the vascular bed. They may also affect the contraction of other smooth muscles other than the vascular smooth muscle. Oxytocin stimulates contraction of the myoepithelium in the mammary gland that is necessary for milk ejection. 

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