Pheochromocytoma cells norepinephrine

In smooth muscle and skeletal muscle exposed in vitro, maitotoxins cause calcium ion-dependent contraction. Water-soluble maitotoxins increase the calcium ion influx through the excitable membrane. These toxins possess a specific calcium-dependent action, which causes a release of norepinephrine from rat pheochromocytoma cells. This action occurs in... 

Evidence from a number of systems suggests that ion flux plays a role in palytoxin action. In a wide range of systems, palytoxin effects are accompanied by a change in intracellular cation levels. For example, the influx of Na and/or Ca is associated with palytoxin-stimulated contraction of cardiac and smooth muscle, the release of norepinephrine by rat pheochromocytoma (PC12) cells, and the depolarization of excitable membranes 12—15). Palytoxin also induces K efflux from erythrocytes and thus alters ion flux in a nonexcitable membrane system as well 16-19). In both excitable and nonexcitable membranes, the ultimate action of palytoxin has been shown to be dependent on extracellular cations. The palytoxin-induced effects on smooth muscle and erythroctyes can be inhibited by removing Ca from the media, and the palytoxin-induced release of norephinephrine from PC12 cells can be blocked in Na" free media (ii, 14y 18, 20, 21)... 

Pheochromocytoma A tumor arising from chromaffin cells, most commonly found in the adrenal medulla. The tumor causes the adrenal medulla to hypersecrete epinephrine and norepinephrine, resulting in hypertension and other signs and symptoms of excessive sympathetic nervous system activity. The tumor is usually benign but may occasionally be cancerous. 

Vertebrates also show expression of AADC in both neural and non-neural tissues. AADC has been purified from kidney (Christenson et al., 1972), liver (Ando-Yamamoto et al., 1987), adrenal medulla (Albert et al., 1987), and pheochromocytoma (Coge et al., 1989 Ichinose et al., 1989). In the adrenal medulla dopamine is further processed into epinephrine and norepinephrine, which are released from the chromaffin cells during stress to increase heart rate and blood pressure. There are no detectable monoamines in the liver and kidney, and the function of AADC in these tissues is unknown. AADC activity has also been... 

Pheochromocytoma is a tumor of the adrenal medulla or sympathetic ganglion cells. The tumor secretes catecholamines, especially norepinephrine and epinephrine. The patient in the case study at the beginning of the chapter had a left adrenal pheochromocytoma that was identified by imaging. In addition, she had elevated plasma and urinary norepinephrine, epinephrine, and their metabolites, normetanephrine and metanephrine. 

Other cell lines are available for in vitro studies, including the Y1 mouse adrenocortical cell line, with different advantages and disadvantages (for review, see [49]). PC-12 cells are from a rat pheochromocytoma, and they produce norepinephrine and dopamine [60], They have been used to study neuroendocrine signaling of the adrenal medulla and differentiate and stop proliferating following exposure to neural growth factor. Adrenal slices have also been used for short-term experiments, especially those that required the presence of both medulla and cortex, but this model has rarely if ever been used to study toxicity of endocrine disruptors. 

Routine laboratory tests may help to identify secondary hypertension. Baseline hypokalemia may suggest mineralocorticoid-induced hypertension. Protein, blood cells, and casts in the urine may indicate renovascular disease. Some laboratory tests are used specifically to diagnose secondary hypertension. These include plasma norepinephrine and urinary metanephrine concentrations for pheochromocytoma, plasma and urinary aldosterone concentrations for primary aldosteronism, and plasma renin activity, captopril stimulation test, renal vein renins, and renal artery angiography for renovascular disease. 

Seegal RF, Brosch K, Bush, B et al. 1989. Effects of Aroclor 1254 on dopamine and norepinephrine concentrations in pheochromocytoma (PC-12) cells. Neurotoxicology 10 757-764. 

Because the control mechanisms that attempt to maintain blood pressure constant are intact in patients with pheochromocytoma (they are reset in patients with ordinary hypertension), a number of compensatory changes are observed in pheochromocytoma patients tsee Figure 6 ). These include reduced renin, angiotensin, and aldosterone levels in the blood. With the reduced aldosterone effect on the kidney, more salt and water is excreted, reducing blood volume. Since the red cell mass is not affected, hematocrit is often increased. If the tumor releases only norepinephrine, a compensatory bradycardia may also be present, but most patients release enough epinephrine to maintain heart rate at a normal or even increased level. 

Pheochromocytoma A tumor that resembles the adrenal medulla consisting of cells that release varying amounts of norepinephrine, epinephrine, or both into the circulation... 

Unfortunately, other biomolecules besides the target a-receptor also are alkylated. Because of its receptor nonselectivity and toxicity, the use of phenoxybenzamine largely is limited to alleviating the sympathetic effects of pheochromocytoma. This tumor of chromaffin cells of the adrenal medulla produces large amounts of epinephrine and norepinephrine, which are released into the bloodstream, producing hypertension and generalized sympathetic stimulation. 

Pheochromocytomas arise from adrenal medulla chromaffin cells. Pheo-chromocytomas associated with VHL disease synthesize and secrete increased amounts of catecholamines, predominantly norepinephrine (85). Catecholamines are neurotransmitters that regulate the activity and tone of cardiac and vascular smooth muscle. Thus, pheochromocytomas can cause sustained or episodic arterial hypertension (86-89). There is a strong correlation between catecholamine levels and concentrations of TH mRNA in pheochromocytomas (90-92). TH mRNA levels are two- to sixfold higher in various pheochromocytomas, as compared to the levels measured in normal adrenal medullas (90-92). 

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