Attenuation of methylation of catecholamines and treatment with a coenzymeof catechol-O-methyltransferase in spontaneously hypertensive rats (SHR)

We have previously demonstrated that the release of plasma norepinephrine ( NE) in response to blood pressure reduction induced by calcium antagonist w as substantially decreased in spontaneously hypertensive rats (SHR), as com pared to the age-matched normotensive Wistar Kyoto (WKY) rats. Here we exam ined extraneuronal methylation of NE: to normetanephrine (NLN) by catechol- O-methyl-transferase (COMT). In the face of an acute hypotension by benidip ine, the ratio of the increase of NMN to the increase of NE in plasma was l ower in SHR than in WKY rat. The finding suggests that the extraneuronal in activation of the released NE is blunted in SHR, namely, COMT is deactivate d in this hypertensive rats. To define the role of NE methylation in hypert ension, S-adenosyl-L-methionine (SAMe; 1.0 mg/kg, i.v.), a coenzyme of COMT , was administered to SHR. The treatment induced a greater antihypertensive effect, along with a greater decrease of NE and a larger increase of NMN i n SHR. The data suggest that SAMe may be used as a possible remedy for hype rtension.