title: Activation of tyrosine 3-monooxygenase in pheochromocytoma cells by adenosine.
abstract: Adenosine increases the activity of tyrosine 3-monooxygenase in intact pheochromocytoma cells. The effect of adenosine is not dependent upon extracellular Ca2+, and is not accompanied by an increase in catecholamine secretion from the cells. Adenosine deaminase decreases the basal activity of tyrosine 3-monooxygenase, and almost completely abolishes the activation of this enzyme by adenosine. In cells treated with adenosine deaminase, 2-chloroadenosine causes a 2- to 5-fold increase in tyrosine 3-monooxygenase activity. 2-Chloroadenosine produces half-maximal activation at a concentration of 0.1 microM, and maximal activation at 10 microM. Incubation of cells with 2-chloroadenosine produces a stable activation of tyrosine 3-monooxygenase, as measured in vitro. Finally, 3-chloroadenosine increases the content of cAMP in pheochromocytoma cells, and increases the incorporation of 3H into cAMP in cells that have been preincubated with [3H]adenine. This rise in cAMP presumably mediates the activation of tyrosine 3-monooxygenase by 2-chloroadenosine. Adenosine appears to be an endogenous regulator of tyrosine 3-monooxygenase activity in pheochromocytoma cells.
mesh_terms: D015762:2-Chloroadenosine; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D000310:Adrenal Gland Neoplasms / Q000201:enzymology* / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002772:Cholera Toxin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004295:Dihydroxyphenylalanine / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D007700:Kinetics; D009638:Norepinephrine / Q000378:metabolism; D010673:Pheochromocytoma / Q000201:enzymology* / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
chemical_list: D015762:2-Chloroadenosine; D004295:Dihydroxyphenylalanine; D002772:Cholera Toxin; D000242:Cyclic AMP; D014446:Tyrosine 3-Monooxygenase; D000241:Adenosine; D002118:Calcium; D009638:Norepinephrine