Hunter L W, Rorie D K, Tyce G M
Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota 55905.
J Neurochem. 1992 Sep;59(3):972-82. doi: 10.1111/j.1471-4159.1992.tb08338.x.
The overflows of 3,4-dihydroxyphenylalanine, dopamine, noradrenaline, and 3,4-dihydroxyphenylglycol in canine portal vein superfused in vitro were studied before, during, and after depolarization of sympathetic nerve endings. The four compounds were separated from superfusate and from tissue on Sep-Pak C-18 cartridges and quantified by HPLC with electrochemical detection. Physiological and biochemical methods were used to show that the compound released was most probably 3,4-dihydroxyphenylalanine; the identity of the other endogenous compounds has been established previously. Release of 3,4-dihydroxyphenylalanine was calcium and frequency dependent, inhibited by a-m-L-p-tyrosine (an inhibitor of tyrosine hydroxylase) and augmented by 3-hydroxybenzylhydrazine (an inhibitor of aromatic amino acid decarboxylase). The overflows of dopamine, noradrenaline, and 3,4-dihydroxyphenylglycol from the vein were calcium and frequency dependent. It was estimated that under control conditions, approximately 80% of the total 3,4-dihydroxyphenylalanine that was synthesized was directed to catecholamine biosynthesis, approximately 8% overflowed from the vein, and approximately 14% remained unchanged within the tissue. It is concluded that 3,4-dihydroxyphenylalanine and dopamine are released together with noradrenaline and 3,4-dihydroxyphenylglycol from portal vein upon nerve depolarization.
在交感神经末梢去极化之前、期间和之后，研究了体外灌流的犬门静脉中3,4-二羟基苯丙氨酸、多巴胺、去甲肾上腺素和3,4-二羟基苯乙二醇的溢出情况。这四种化合物在Sep-Pak C-18柱上从灌流液和组织中分离出来，并通过高效液相色谱电化学检测进行定量。采用生理生化方法表明，释放出的化合物很可能是3,4-二羟基苯丙氨酸；其他内源性化合物的身份先前已确定。3,4-二羟基苯丙氨酸的释放依赖于钙和频率，受α-m-L-对酪氨酸（酪氨酸羟化酶抑制剂）抑制，并被3-羟基苄肼（芳香族氨基酸脱羧酶抑制剂）增强。静脉中多巴胺、去甲肾上腺素和3,4-二羟基苯乙二醇的溢出依赖于钙和频率。据估计，在对照条件下，合成的总3,4-二羟基苯丙氨酸中约80%用于儿茶酚胺生物合成，约8%从静脉中溢出，约14%在组织内保持不变。结论是，在神经去极化时，3,4-二羟基苯丙氨酸和多巴胺与去甲肾上腺素和3,4-二羟基苯乙二醇一起从门静脉释放。
