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MONOAMINE OXIDASE A AND B IN CULTURED CELLS
Author(s) -
Hawkins Morris,
Breakefield Xandra O.
Publication year - 1978
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1978.tb10471.x
Subject(s) - clorgyline , tryptamine , monoamine oxidase , neuroblastoma , monoamine oxidase b , monoamine oxidase a , biochemistry , chemistry , iproniazid , biology , microbiology and biotechnology , enzyme , cell culture , genetics
— Monoamine oxidase (MAO) activity against tryptamine was compared in a number of continuous rodent lines, including neuroblastoma, hepatoma, melanoma, nephroma, sarcoma and L cells. Activities against tryptamine varied over 300‐fold in homogenates of different lines, being highest in hepatoma line MH 1 C 1 and lowest in a neuroblastoma line lacking hypoxanthine phosphoribosyltransferase (HPRT) activity. The amount, but not the type, of MAO activity varied with the stage of growth in homogenates of neuroblastoma and hepatoma cells. Measurements of succinate‐cytochrome c reductase (SCCR), another mitochondrial enzyme, also showed 20‐fold variations between lines, being highest in neuroblastoma line N1E‐115 and lowest in hepatoma line MH 1 C 1 ; SCCR and MAO activities appeared to be regulated independently. The relative proportions of the A and B types of MAO activity were determined in homogenates and living cultures. Clorgyline inhibition of tryptamine deamination in homogenates indicated that in all lines except MH 1 C 1 , greater than 95% of the MAO activity was of the A type. In MH 1 C 1 homogenates, using clorgyline or deprenyl, 40–70% of the activity appeared to be of the A type and 30‐60% of the B type. In cultures of neuroblastoma N1E‐115 cells, deamination of tryptamine and dopamine was sensitive to inhibition by low concentrations of clorgyline, indicating that the A type of activity is present intracellularly. as in homogenates. In MH 1 C 1 hepatoma cultures, tryptamine deamination showed a biphasic sensitivity to clorgyline. We interpret this to mean that A and B types of MAO activity occur together in living hepatoma cells.