title: Reduction in beta-adrenergic response of cultured glioma cells following depletion of intracellular GTP.
abstract: 1. When C6 glioma cells were incubated with mycophenolic acid, a potent and specific inhibitor of IMP:NAD oxidoreductase (EC 1.2.1.14) there was a marked depletion of the cellular content of GTP. The viability of the cells was unaffected. 2. The adenosine 3':5'-monophosphate (cyclic AMP) response of C6 glioma cells to the beta-adrenergic stimulant, (+/-)isoprenaline, was considerably reduced after treatment with mycophenolic acid. The diminished response to (+/-)isoprenaline was prevented by the inclusion of guanine in the culture medium along with mycophenolic acid. 3. The adenylate cyclase response to (+/-)isoprenaline of whole homogenates from C6 cells treated with mycophenolic acid was also depressed; the response was restored to normal by the addition of GTP. 4. The adenylate cyclase response to (+/-)isoprenaline of a membrane fraction prepared from homogenates of C6 cells was almost totally dependent on the presence of added GTP. Membrane fractions from control and mycophenolic-acid-treated C6 cells gave similar adenylate cyclase responses to (+/-)isoprenaline in the presence of GTP. 5. It is concluded that mycophenolic acid may depress the beta-adrenergic sensitivity of C6 cells by depleting the cellular content of GTP.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D000242:Cyclic AMP / Q000378:metabolism*; D004789:Enzyme Activation; D005910:Glioma / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology*; D007700:Kinetics; D009173:Mycophenolic Acid / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D009173:Mycophenolic Acid; D007545:Isoproterenol