Smooth muscle Vascular system

Endothelin has many other biological actions, but among the most important of these are the effects on the airways, the gastro-intestinal tract, the kidney and the central nervous system. In addition to its effects on the pulmonary circulation, endothelin has marked effects on non-vascular airway smooth muscle. ET-1 is a potent constrictor of guinea-pig isolated trachea, upper bronchus and parenchyma [35]. ET-2 and ET-3 also contract isolated guinea-pig trachea, although ET-3 is less potent than the other two isoforms [36]. Endothelin contracts bronchial smooth muscle from a... 

Lead is toxic to the kidney, cardiovascular system, developiag red blood cells, and the nervous system. The toxicity of lead to the kidney is manifested by chronic nephropathy and appears to result from long-term, relatively high dose exposure to lead. It appears that the toxicity of lead to the kidney results from effects on the cells lining the proximal tubules. Lead inhibits the metaboHc activation of vitamin D in these cells, and induces the formation of dense lead—protein complexes, causing a progressive destmction of the proximal tubules (13). Lead has been impHcated in causing hypertension as a result of a direct action on vascular smooth muscle as well as the toxic effects on the kidneys (12,13). 

ANPs play an important role in the maintenance of cardiovascular homeostasis by counterbalancing the renin—angiotensin (RAS) system. ANP, the main circulating form of the natriuretic peptides, effectively relaxes vascular smooth muscle, promotes the excretion of sodium and water, and in the CNS inhibits vasopressin release and antagonizes AT-II induced thirst. 

The resting membrane potential of most excitable cells is around —60 to —80 mV. This gradient is maintained by the activity of various ion channels. When the potassium channels of the cell open, potassium efflux occurs and hyperpolari2ation results. This decreases calcium channel openings, which ia turn preveats the influx of calcium iato the cell lea ding to a decrease ia iatraceUular calcium ia the smooth muscles of the vasculature. The vascular smooth muscles thea relax and the systemic blood pressure faUs. 

Sites of endothelin-receptor expression. ETA receptors are expressed in the smooth muscle cells of the vascular medial layer and the airways, in cardiac myocytes, lung parenchyma, bronchiolar epithelial cells and prostate epithelial cells. ETB receptors are expressed in endothelial cells, in bronchiolar smooth muscle cells, vascular smooth muscle cells of certain vessels (e.g. saphenous vein, internal mammary artety), in the renal proximal and distal tubule, the renal collecting duct and in the cells of the atrioventricular conducting system. 

In the vascular system, endothelial ETB receptors mediate a transient vasodilation, whereas ETA receptors cause a long-lasting vasoconstriction. The role of ETb receptors expressed on smooth muscle cells... 

Histamine is a substance present in various tissues of die body, such as die heart, lungs, gastric mucosa, and skin (Pig. 36-1). The highest concentration of histamine is found in die basophil (a type of white blood cell) and mast cells diat are found near capillaries. Histamine is produced in response to injury. It acts on areas such as die vascular system and smooth muscle, producing dilatation of arterioles and an increased permeability of capillaries and venules. Dilatation of die arterioles results in localized redness. An increase in die permeability of... 

Systemic and coronary arteries are influenced by movement of calcium across cell membranes of vascular smooth muscle. The contractions of cardiac and vascular smooth muscle depend on movement of extracellular calcium ions into these walls through specific ion channels. Calcium channel blockers, such as amlodipine (Norvasc), diltiazem (Cardizem), nicardipine (Cardene), nifedipine (Procardia), and verapamil (Calan), inhibit die movement of calcium ions across cell membranes. This results in less calcium available for the transmission of nerve impulses (Fig. 41-1). This drug action of the calcium channel blockers (also known as slow channel blockers) has several effects on die heart, including an effect on die smooth muscle of arteries and arterioles. These drug dilate coronary arteries and arterioles, which in turn deliver more oxygen to cardiac muscle. Dilation of peripheral arteries reduces die workload of die heart. The end effect of these drug is the same as that of die nitrates. 

Because of its motor, i.e., activating effect on vascular smooth muscle and its inhibitory effect on intestinal smooth muscle, the sympathetic nervous system has been cast into the role of the component of the nervous system that executes control of visceral function in times of physical emergency for the organism. The phrase fight or flight has been often used to describe the circumstances in which the adrenergic transmitters of the sympathetic system are dominant over the cholinergic parasympathetic system. This concept is perhaps oversimplified but it has the utility of a first approximation of how the two components of the ANS interact in the periphery. Sensory inputs which lead to increased blood pressure, for example, activate the sympathetic pathways. 

Renal Effects. Acute nephrosis has been reported in humans after acute, lethal intoxication (Fazekas 1971) by methyl parathion (Wofatox). This may be a secondary effect of hypoxia related to the neurologic effects of methyl parathion on vascular smooth muscle and on the electrical conduction system of the heart. It could also be related to therapeutic efforts. 

Another example was done by Opitz et al. They utilized P4HB scaffolds to produce viable ovine blood vessels, and then implanted the blood vessels in the systemic circulation of sheep. Enzymatically derived vascular smooth muscle cells (vSMC) were seeded on the scaffolds both under pulsatile flow and static conditions. Mechanical properties of bioreactor-cultured blood vessels which were obtained from tissue engineering approached those of native aorta. 

Psychogenic dysfunction occurs if a patient does not respond to psychic arousal. It occurs in up to 30% of all cases of ED. Common causes include performance anxiety, strained relationships, lack of sexual arousability, and overt psychiatric disorders such as depression and schizophrenia.5 It is postulated that the anxious or nervous man will have excessive stimulation of the sympathetic system, leading to smooth muscle contraction of arterioles and vascular spaces within erectile tissue.6 O Many patients may initially have organic dysfunction, but develop a psychogenic component as they try to cope with their inability to achieve an erection. It has been estimated that up to 80% of ED cases have an organic cause, with many having a psychogenic component as well.1... 

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