Brownfield M S, Poff B C, Holzwarth M A
Histochemistry. 1985;83(1):41-6. doi: 10.1007/BF00495298.
Previous immunocytochemical studies at the light microscopic level have demonstrated serotonin immunoreactivity in rat adrenal epinephrine-containing cells. In this study we have used electron microscopic immunocytochemical methods to study the subcellular distribution of serotonin and the enzyme responsible for epinephrine biosynthesis, phenylethanolamine-N-methyltransferase (PNMT). The distribution of the immunostaining was compared in adjacent serial thin sections using a post-embedding method in conjunction with peroxidase-antiperoxidase (PAP) immunocytochemistry. Serotonin immunoreactivity was associated with the limiting membrane as well as with the core of the chromaffin vesicles. In adjacent sections PNMT immunoreactivity was also seen in the serotonin-containing vesicles. However, its intravesicular distribution was different from that of serotonin; PNMT occupied the eccentric zone of the vesicles between the serotonin immunoreactive sites. These results are interpreted to be in support of biochemical studies claiming a serotonin uptake and storage capacity of adrenal chromaffin vesicle fractions as well as those which suggest serotonin is synthesized by chromaffin cells. The relative contribution of uptake and synthesis to the pool of serotonin that is stored in the vesicles is an open question. The co-localization of serotonin and PNMT in the same vesicle is suggestive of a capacity for co-release of serotonin and epinephrine by the adrenal medulla.
以往在光学显微镜水平进行的免疫细胞化学研究已证实，大鼠肾上腺含肾上腺素细胞中存在5-羟色胺免疫反应性。在本研究中，我们采用电子显微镜免疫细胞化学方法，研究了5-羟色胺以及负责肾上腺素生物合成的酶——苯乙醇胺-N-甲基转移酶（PNMT）的亚细胞分布。使用包埋后方法结合过氧化物酶-抗过氧化物酶（PAP）免疫细胞化学，在相邻的连续薄切片中比较了免疫染色的分布。5-羟色胺免疫反应性与嗜铬小泡的界膜以及核心相关。在相邻切片中，在含5-羟色胺的小泡中也可见PNMT免疫反应性。然而，其在小泡内的分布与5-羟色胺不同；PNMT占据了5-羟色胺免疫反应位点之间小泡的偏心区域。这些结果被解释为支持生化研究，这些研究表明肾上腺嗜铬小泡组分具有摄取和储存5-羟色胺的能力，以及那些提示5-羟色胺由嗜铬细胞合成的研究。摄取和合成对储存在小泡中的5-羟色胺池的相对贡献仍是一个未解决的问题。5-羟色胺和PNMT在同一小泡中的共定位提示肾上腺髓质具有共同释放5-羟色胺和肾上腺素的能力。
