Schanberg S M, Schildkraut J J, Breese G R, Kopin I J
Biochem Pharmacol. 1968 Feb;17(2):247-54. doi: 10.1016/0006-2952(68)90330-4.
Normetanephrine-H injected into the cisterna magna of rats is rapidly metabolized and disappears from brain with an initial half-life of about 12 min. Monoamine oxidase inhibition prevents almost completely the conversion of normetanephrine-H to other metabolites and markedly diminishes the rate of disappearance of radioactivity from brain ( ). These data show that normetanephrine is normally metabolized primarily by monoamine oxidase and that unaltered normetanephrine does not readily pass out of the brain. Free 3-methoxy-4-hydroxyphenylglycol (MHPG) and 3-methoxy-4-hydroxymandelic acid (VMA) formed from intracistemally injected normetanephrine-H represent only a small fraction of the radioactivity in brain. The major metabolite was identified as the sulfate conjugate of MHPG. After intracisternal administration of norepinephrine-H, 3-methoxy-4-hydroxyphenylgIycol sulfate (MHPG-SO) was also found to be the major metabolite present in brain. These findings suggest that deamination, reduction, and subsequent corrugation with sulfate is the primary route of metabolism of normetanephrine in rat brain and that norepinephrine is also metabolized to this sulfate conjugate.
注入大鼠脑池的去甲变肾上腺素 - H迅速代谢，从脑中消失，初始半衰期约为12分钟。单胺氧化酶抑制几乎完全阻止去甲变肾上腺素 - H转化为其他代谢产物，并显著降低脑中放射性消失的速率（ ）。这些数据表明，去甲变肾上腺素通常主要由单胺氧化酶代谢，且未改变的去甲变肾上腺素不易从脑中排出。由脑池内注射的去甲变肾上腺素 - H形成的游离3 - 甲氧基 - 4 - 羟基苯乙二醇（MHPG）和3 - 甲氧基 - 4 - 羟基扁桃酸（VMA）仅占脑中放射性的一小部分。主要代谢产物被鉴定为MHPG的硫酸盐结合物。脑池内给予去甲肾上腺素 - H后，3 - 甲氧基 - 4 - 羟基苯乙二醇硫酸盐（MHPG - SO）也被发现是脑中存在的主要代谢产物。这些发现表明，脱氨基、还原以及随后与硫酸盐结合是大鼠脑中去甲变肾上腺素的主要代谢途径，并且去甲肾上腺素也代谢为这种硫酸盐结合物。
