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Monoamine Oxidase in Rat and Bovine Endocrine
Author(s) -
Lenzen Tissues Sigurd,
FreisingerTreichel Marion,
Panten Uwe
Publication year - 1987
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.1471-4159.1987.tb10009.x
Subject(s) - monoamine oxidase , endocrinology , medicine , adrenal medulla , clorgyline , biology , medulla , adrenal cortex , pancreatic islets , oxidative deamination , chemistry , biochemistry , enzyme , islet , catecholamine , insulin
Monoamine oxidase (MAO) was characterized in tissue homogenates from rat pancreatic islets, rat neurohy‐pophysis and adenohypophysis, and rat and bovine adrenal medulla and adrenal cortex. Phenylethylamine was preferentially deaminated by rat pancreatic islet and bovine adrenal medulla MAO and with slight preference by rat neurohypophysis MAO, whereas 5‐hydroxytryptamine was preferentially deaminated by MAO from all other endocrine tissues. Tyramine was a good substrate for all tissues. Clor‐gyline, a selective inhibitor of MAO‐A, preferentially inhibited deamination of 5‐hydroxytryptamine by all tissue homogenates, whereas deprenyl, a selective inhibitor of MAO‐B, preferentially inhibited deamination of phenyl‐ethylamine. K m values for 5‐hydroxytryptamine and tyra‐mine were higher by one to two decimal powers than for phenylethylamine in homogenates from all endocrine tissues. K m values were significantly lower for 5‐hydroxytryptamine and significantly higher for phenylethylamine in rat and bovine adrenal cortex than in adrenal medulla. According to these results, the contributions of MAO‐B to total enzyme activity were 70% for rat pancreatic islets, 45% for rat neurohypophysis, 15% for rat adenohypophysis, 20% for rat adrenal medulla, 10% for rat adrenal cortex, 60% for bovine adrenal medulla, and 20% for bovine adrenal cortex. PC 12 cells also contained predominantly MAO‐A (90%); however, an increased K m for phenylethylamine and a sensitivity of deamination of this MAO‐B substrate to inhibition by clorgyline are indicators of abnormal behavior of MAO in this clonal rat pheochromocytoma cell line.