Devine C E, Simpson F O
J Cell Biol. 1968 Jul;38(1):184-92. doi: 10.1083/jcb.38.1.184.
The distribution of infused tritiated norepinephrine (NE-(3)H) in small mesenteric arteries and intestinal arterioles in rats was investigated with electron microscopic radioautography. Silver grains, indicating the presence of the tritium label on the sections, were found lying mainly over axon bundles, but some were present over collagen and smooth muscle cells. Axons with the highest concentrations of silver grains had been sectioned at points where they were naked of Schwann cell sheath, were dilated into varicosities, and contained small granular vesicles. This finding was taken as confirmatory circumstantial evidence that the small granular vesicles were the sites of uptake and storage of NE. The short interval between the start of infusion and the fixation of the tissue appeared to rule out any process other than a direct uptake of NE by the peripheral axons. If axonal sites of uptake of NE-(3)H correspond to sites of release of NE, then the evidence suggests that such sites of release are widespread over the terminal part of the axon and are not confined to those parts of the axon which are in close contact with smooth muscle cells. Since the fixation and embedding procedures will remove NE which is not strongly bound to tissues, the localization of NE-(3)H in the radioautographs does not necessarily correspond to the distribution of all the NE present in vivo.
用电子显微镜放射自显影术研究了注入大鼠体内的氚标记去甲肾上腺素（NE-(3)H）在肠系膜小动脉和肠小动脉中的分布。切片上显示存在氚标记的银颗粒主要位于轴突束上，但也有一些存在于胶原纤维和平滑肌细胞上。银颗粒浓度最高的轴突在没有施万细胞鞘的部位被切断，扩张成膨体，并含有小颗粒囊泡。这一发现被视为间接的确证证据，表明小颗粒囊泡是去甲肾上腺素摄取和储存的部位。从开始注入到组织固定之间的短时间间隔似乎排除了除外周轴突直接摄取去甲肾上腺素之外的任何过程。如果氚标记去甲肾上腺素（NE-(3)H）的轴突摄取部位与去甲肾上腺素的释放部位相对应，那么证据表明这种释放部位广泛分布于轴突的末端部分，并不局限于与平滑肌细胞紧密接触的轴突部分。由于固定和包埋程序会去除未与组织紧密结合的去甲肾上腺素，放射自显影片中氚标记去甲肾上腺素（NE-(3)H）的定位不一定与体内所有去甲肾上腺素的分布相对应。
