Showing papers on "Catechol-O-methyl transferase published in 1983"
TL;DR: Results indicate that the Km membrane‐bound catechol‐O‐methyltransferase may be localized predominantly in neurons, whereas the high‐Km soluble enzyme is found in glial cells.
Abstract: The cellular localization of the two forms of catechol-O-methyltransferase (COMT) was investigated by measuring their activities in rat striatum following unilateral stereotaxic injection of kainic acid, which causes degeneration of striatal neurons followed by proliferation of astroglial cells. Membrane-bound COMT activity was decreased in the lesioned striatum, while soluble COMT activity was increased. There was a statistically significant correlation between the ratio of lesioned to control activity for membrane-bond COMT and the neuronal marker enzyme glutamate decarboxylase. Similarly the increase in soluble COMT activity paralleled that of the astroglial marker enzyme, glutamine synthetase. These results indicate that the low-Km membrane-bound catechol-O-methyltransferase may be localized predominantly in neurons, whereas the high-Km soluble enzyme is found in glial cells.
112 citations
TL;DR: Cultures from cerebral heimspheres of newborn rats contain the enzymes monoamine oxidase, catechol‐O‐methyltransferase (COMT), and α‐aminobutyric acid γ‐ketoglutarate transaminase (GABA‐T).
Abstract: Cultures from cerebral hemispheres of newborn rats contain the enzymes monoamine oxidase (MAO), catechol-O-methyltransferase (COMT), and gamma-aminobutyric acid alpha-ketoglutarate transaminase (GABA-T). The COMT activity was higher in the cultures than in adult rat cerebral hemispheres. The MAO activity was comparable in the cultures and in the rat cerebral hemispheres. The activities of both these enzymes increased with age in the cultures and in the rat brain hemispheres. In the culture the activities were further potentiated by removal of fetal calf serum and addition of 0.1 mM dibutyryl-cyclic AMP (dB-cAMP). GABA-T activity was, however, lower in the cultures than in the adult rat brain hemispheres. The activity increased in brain during postnatal maturation. No changes in the enzyme activity were observed in the cultures, either during growth or after removal of fetal calf serum and addition of dB-cAMP.
48 citations
TL;DR: It seems likely that the two forms of COMT have different functions in vivo, with the highest ratio in brain being the likely destination for membrane‐bound activity.
Abstract: Previous studies of the distribution of catechol-O-methyltransferase (COMT) have concentrated on the soluble enzyme activity. In this study the activity of the membrane-bound enzyme was determined in different brain regions and peripheral tissues of the rat. Membrane-bound COMT, like the soluble enzyme, has a general distribution with high levels in liver, kidney, and vas deferens. However, the ratio of membrane-bound to soluble activity varies almost 30-fold in different tissues, with the highest ratio in brain. Membrane-bound activity varies twofold within brain. In view of their different localization and kinetic properties, it seems likely that the two forms of COMT have different functions in vivo.
47 citations
01 Jan 1983
TL;DR: It is concluded that the reduced activities of PNMT, COMT and MAO following 6 weeks swimming do not arise from stress elicited by the present swimming routine, but can be attributed to the effects of exercise, such as reduced sympathetic nerve activity.
Abstract: The activities of catecholamine enzymes have been determined in adrenal glands of Wistar rats following 2 and 6 weeks of intermittent swimming (max. 2 × 90 min daily in 35 °C warm water) and 6 weeks intermittent experimentally induced emotional excitation (“shock-induced aggression”)- Following 2 weeks swimming, there was no significant change in activities of phenylethanolamine-N-methyltrans-ferase (PNMT) and catechol-O-methyltransferase (COMT); monoamine oxidase (MAO) activity was significantly increased. In contrast, a swimming routine extending over 6 weeks resulted in significantly reduced activities of PNMT, COMT, and MAO. Intermittent emotional excitation of the same time-course extending over 6 weeks did not significantly affect the enzyme activities. Qualitatively similar changes were observed in the heart. It is concluded that the reduced activities of PNMT, COMT and MAO following 6 weeks swimming do not arise from stress elicited by the present swimming routine, but can be attributed to the effects of exercise, such as reduced sympathetic nerve activity.
8 citations
Journal Article•
TL;DR: The immunocytochemical identification of a strong activity of COMT in all cases studied might have a diagnostic implication in breast cancer.
Abstract: Immunoperoxidase reaction of appropriately fixed tissue with an antiserum to catechol-o-methyl transferase (COMT), as the primary step in the peroxidase-immunoglobulin bridge technique, has been utilized for the localization of COMT in biopsy specimens of human breast neoplasm and its metastases. Our immunocytochemical identification of a strong activity of COMT in all cases studied might have a diagnostic implication in breast cancer.
2 citations
01 Jan 1983
TL;DR: In this article, the effect of altered thyroid hormone status on myosin heterogeneity and catecholamine enzymes was investigated in ventricles and atria of the rat heart.
Abstract: The effect of altered thyroid hormone status on myosin heterogeneity and catecholamine enzymes was investigated in ventricles and atria of the rat heart. Hypothyroidism (0.08 % propylthiouracil in drinking water for 6 weeks) and hyper-thyroidism (daily 1 mg/kg thyroxine intraperitoneally for 2 weeks) resulted in homogeneous ventricular myosin (VM)-3 and VM-1, respectively, in rat ventricles. No such marked changes in the isoenzyme population were observed in atrial myosins using also as criterion the separation by non-dissociating pyrophosphate gel electrophoresis. Since the ventricular myosin isoenzyme population can additionally be altered by adrenergic agonists, the catecholamine enzymes phenyl-ethanolamine-N-methyltransferase (PNMT), catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) were studied in ventricles versus atria of hypothyroid and hyperthyroid rats. As in the case of myosin isoenzymes, the response of PNMT, COMT and MAO to altered circulating thyroid hormones was different when determined in ventricles compared to atria. In ventricles, PNMT, COMT, and MAO activities were significantly reduced in hyperthyroid rats compared to hypothyroid rats, whereas an opposite change was found in atria: the enzyme activities were higher for the hyperthyroid relative to the hypothyroid state. The results suggest that ventricles and atria of rat heart differ in their response towards circulating thyroid hormones not only with respect to myosin heterogeneity, but also to catecholamine enzymes. The different action of altered thyroid status on catecholamine metabolism could thus be considered a factor contributing to the expression of the above myosin isoenzyme populations.
1 citations