Russell J A, Kircher K W
J Appl Physiol (1985). 1985 Oct;59(4):1236-41. doi: 10.1152/jappl.1985.59.4.1236.
We determined the relative importance of neuronal and extraneuronal uptake in the metabolism of norepinephrine (NE) released during electrical stimulation (ES) of isolated canine tracheal smooth muscle (TSM). Strips of TSM were labeled with L-[3H]NE (2 X 10(-7) M) and mounted for superfusion. Superfusate was collected continuously before, during, and after ES (15 V, 0.5 ms, 5 Hz). Measurements were made of [3H]NE and its metabolites in superfusate and in tissue. Neuronal uptake followed by metabolism was estimated by measuring the amount of 3,4-dihydroxyphenylglycol (DOPEG). Extraneuronal uptake was estimated by measuring O-methylated metabolites (OMM). ES caused large increases in the efflux of NE, DOPEG, and OMM from TSM. However, the overflow of OMM was six times greater than that of DOPEG. Cocaine (10(-5) M) abolished the increased efflux of DOPEG during ES and enhanced the overflow of NE and OMM. We conclude that extraneuronal uptake constitutes the primary metabolic pathway for NE released from adrenergic nerves innervating TSM.
我们确定了在离体犬气管平滑肌（TSM）电刺激（ES）过程中释放的去甲肾上腺素（NE）代谢过程中神经元摄取和非神经元摄取的相对重要性。TSM条带用L-[3H]NE（2×10⁻⁷M）标记并安装用于灌流。在ES（15V，0.5ms，5Hz）之前、期间和之后连续收集灌流液。对灌流液和组织中的[3H]NE及其代谢产物进行测量。通过测量3,4-二羟基苯乙二醇（DOPEG）的量来估计神经元摄取后代谢的情况。通过测量O-甲基化代谢产物（OMM）来估计非神经元摄取。ES导致TSM中NE、DOPEG和OMM的流出大幅增加。然而，OMM的溢出比DOPEG的溢出大六倍。可卡因（10⁻⁵M）消除了ES期间DOPEG流出的增加，并增强了NE和OMM的溢出。我们得出结论，非神经元摄取是支配TSM的肾上腺素能神经释放的NE的主要代谢途径。
