Rat liver and kidney catechol‐<i>O</i>‐methyltransferase activity measured by high‐performance liquid chromatography with fluorescence detection

Tsunoda, Makoto; Takezawa, Kazuko; Masuda, Mayumi; Imai, Kazuhiro

doi:10.1002/bmc.202

Cited by 28 publications

(23 citation statements)

References 35 publications

(9 reference statements)

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“…The S-COMT activities in both tissues were lower in the normotensive DS rats than in DR rats fed a NS diet, which suggests that the S-COMT activities in those tissues are lower in DS rats than in DR rats, and that this difference is genetic. The K m values of S-COMT for NE in both tissues of all groups were 20-30 times higher than those of MB-COMT, consistent with the findings reported in a previous study ( 26 ). This result indicates that MB-COMT has higher affinity for NE than S-COMT and plays a more important role in metabolizing NE even considering that the activities of S-COMT are 5-10 times higher than those of MB-COMT.…”

Section: Discussionsupporting

confidence: 91%

Suppression of Catechol-O-Methyltransferase Activity through Blunting of .ALPHA.2-Adrenoceptor Can Explain Hypertension in Dahl Salt-Sensitive Rats

et al. 2007

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Section: Discussionsupporting

confidence: 91%

Suppression of Catechol-O-Methyltransferase Activity through Blunting of .ALPHA.2-Adrenoceptor Can Explain Hypertension in Dahl Salt-Sensitive Rats

et al. 2007

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“…There were no differences in the affinity for NE in both isozymes. In both SHR and WKY rats, the Km values for NE in S-COMT were about 80 times higher than those in MB-COMT, which is in agreement with the previous reports (13,14,17). The Vmax/Km values, i.e., the specificity constant values were calculated based on the above data.…”

Section: Km Values For Ne In the Liversupporting

confidence: 74%

“…The general procedure for the COMT activity measurement in tissues and erythrocytes was similar to that previously described (13,14). Tissues were removed from anesthetized rats, weighed, and homogenized in homogenizing buffer (50 mmol/l sodium phosphate buffer (pH 7.5) with 0.5 mmol/l dithiothreitol).…”

Section: Comt Activity and Kinetics Measurementmentioning

confidence: 99%

Reduced Membrane-Bound Catechol-O-Methyltransferase in the Liver of Spontaneously Hypertensive Rats

et al. 2003

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We have previously reported that methylation of catecholamines by catechol-O-methyltransferase (COMT)washighly sensitive method to measure NE and NMN (7-9). Using this method, we demonstrated that methylation of catecholamines by COMT in SHR was attenuated during acute hypotension, when compared to that in WKY rats. Furthermore, intravenous administration of S-adenosyl-L-methionine (SAMe), a coenzyme for COMT, lowered blood pressure in SHR with a concomitant increase of NMN (10).Since COMTs exist in most tissues in a soluble form (S-COMT) as well as a membrane-bound form (MB-COMT), it is important to examine whether one of these subtypes plays a more crucial role than the other in the inactivation of released NE. Therefore, we determined S-and MB-COMT enzyme activities and the amount of protein in two representative rat tissues-the liver and kidney-as well as in erythrocytes. To examine the correlation between these enzymes and hypertensive states, pre-hypertensive SHR (4 weeks of age), hypertensive adult SHR (23 weeks of age), and agematched normotensive WKY rats were used.

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“…[14][15][16] However, there is a difference in their magnitudes: MB-COMT activities were only 2-5 times lower than S-COMT activities in the brain but were 15-25 times lower in the liver and the kidney. Considering the results obtained in the difference of affinities for COMT described below, MB-COMT in the brain may play a more important role than other peripheral tissues.…”

Section: Discussionmentioning

confidence: 95%

Low Catechol-O-methyltransferase Activity in the Brain and Blood Pressure Regulation

Masuda

Tsunoda

Imai

2006

Biological & Pharmaceutical Bulletin

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Catechol-O-methyltransferase (COMT; EC2.1.1.6) is an enzyme which inactivates the released catecholamines from nerve endings by methylating their catechol moieties using S-adenosyl-L-methionine (SAMe) as a methyl donor. [1][2][3][4] COMT is found in most mammalian tissues, with highest activity in the liver and the kidney. There are two COMT isoforms: in the cytoplasm as soluble COMT (S-COMT) and in association with membranes as membrane-bound COMT (MB-COMT). S-COMT protein is more prevalent than MB-COMT in all tissues in rats. 5)Catecholamines, norepinephrine (NE), dopamine and epinephrine, play important roles in the central nervous system as in the periphery, 6) and in central regions, catecholaminesrelated gene expression was correlated with blood pressure. 7)We have previously reported an assay method for rat brain COMT activities, using NE as an endogenous substrate. 8)The use of the endogenous substrate provides significant information of COMT in vivo as compared with formerly reported method which uses an artificial substrate, 3,4-dihydroxybenzoic acid (DBA). Endogenous NE has higher affinity for COMT than DBA, and our method is more sensitive to measure COMT activity. In this study, COMT activities were evaluated in cerebral cortex, cerebellum, hippocampus, brain stem, hypophysis, and hypothalamus in order to evaluate the role of COMT in blood pressure regulation using spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. In addition, in order to investigate the contribution of COMT activities to NE metabolism, NE and its 3-Omethyl metabolite, normetanephrine (NMN), concentrations were examined in discrete areas of SHR and WKY rats. MATERIALS AND METHODSReagent NE, NMN, SAMe chloride salt and 4-methoxytyramine (4-MT) were obtained from Sigma (St. Louis, MO, U.S.A.). Ethylenediamine was obtained from Sigma-Aldrich (Milwaukee, WI, U.S.A.). Imidazole and 1,4-dithiothreitol were from Merck (Darmstadt, Germany). Acetonitrile and ethanol, both of HPLC grade, were purchased from Wako Pure Chemicals (Osaka, Japan). All other reagents were of analytical grade.Animals Male WKY rats (22 weeks old, 405-415 g) and SHR (22 weeks old, 330-350 g) were purchased from Charles River Japan Inc. (Kanagawa, Japan), and housed under controlled environment (22-24°C and a 12-h light-dark cycle) with free access to tap water and diet for at least 1 week before study. All animals received animal care in compliance with the National Institute of Health guideline.Preparation of Brain COMT Samples In anesthetized rats with pentobarbital, blood was removed from inferior vena cava, and cerebral cortex, cerebellum, hippocampus, brain stem, hypophysis and hypothalamus were immediately removed and chilled on ice. All further procedures were conducted at 4°C. Each tissue was weighed and then homogenized with four volumes of 50 mmol/l sodium phosphate buffer containing 0.5 mmol/l 1,4-dithiothreitol (pH 7.5). The homogenates were centrifuged at 100000ϫg for 30 min and the supernatants were stored for the determination of S-COMT...

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Rat liver and kidney catechol‐O‐methyltransferase activity measured by high‐performance liquid chromatography with fluorescence detection

Cited by 28 publications

References 35 publications

Suppression of Catechol-O-Methyltransferase Activity through Blunting of .ALPHA.2-Adrenoceptor Can Explain Hypertension in Dahl Salt-Sensitive Rats

Suppression of Catechol-O-Methyltransferase Activity through Blunting of .ALPHA.2-Adrenoceptor Can Explain Hypertension in Dahl Salt-Sensitive Rats

Reduced Membrane-Bound Catechol-O-Methyltransferase in the Liver of Spontaneously Hypertensive Rats

Low Catechol-O-methyltransferase Activity in the Brain and Blood Pressure Regulation

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