MONOAMINE-OXIDASE AND SEMICARBAZIDE-SENSITIVE AMINE OXIDASE ACTIVITIES IN ISOLATED CARDIOMYOCYTES OF SPONTANEOUSLY HYPERTENSIVE RATS

In the isolated cardiomyocytes of spontaneously hypertensive rats (SHR , 3 months old) MAO A and B activities were significantly increased co mpared to the myocytes in the hearts of age-matched Wistar-Kyoto rats. This increase was not associated with cardiac hypertrophy in these yo ung animals, but might represent an early event in the development of hypertrophy. A semicarbazide-sensitive amine oxidase (SSAO) activity w as found in cardiomyocytes. This activity showed a high affinity for b enzylamine (K-m 5-6 mu M) and was not inhibited by 10(-4) M pargyline and 10(-5) M deprenyl, but was largely inhibited by 10(-4) M B-24 (3,5 -diethoxy-4-aminomethylpyridine), a specific inhibitor of semicarbazid e-sensitive amine oxidase with high affinity for benzylamine. The SSAO enzyme of rat cardiomyocytes is a copper-amine oxidase and has a cros sreactivity with the antibodies raised against pure pig plasma benzyla mine oxidase. In the cardiomyocytes of 3-month-old SHR rats the level of this enzymic activity is not significantly increased. (C) 1997 Acad emic Press.