Biol. Pharm. Bull. 30(11) 2178—2180 (2007)

and epinephrine) play important roles not only in the peripheral nervous system but in the central one. One of the inactivation pathways of CAs is the enzymatic metabolism by catechol-O-methyltransferase (COMT; EC2.1.1.6), which methylates their catechol moieties using S-adenosyl-L-methionine (SAMe) as a methyl donor. There are two COMT isoforms: in the cytoplasm as soluble COMT (S-COMT) and in association with membranes as membrane-bound COMT (MB-COMT). We have previously reported a rapid assay method for COMT activities using high-performance liquid chromatography (HPLC)-fluorescence detection. In this study, we applied the method to brain tissues, such as cerebral cortex, cerebellum, hypophysis and hypothalamus. In previous report using Sprague-Dawley (SD) rats, the cerebral cortex and the cerebellum were seemed to be important parts in brain for the metabolism of NE. Furthermore, the experiment with spontaneously hypertensive rats (SHR) suggested an association between MB-COMT in the cerebral cortex and blood pressure. Hence, in order to clarify the role of COMT in rat brain in relation to salt-sensitive hypertension, COMT activities in Dahl salt-sensitive (DS) rats, which are model rats of salt-sensitive hypertension, were also examined.