小鼠胸腺皮质5′-核苷酸酶的细胞化学定位

用Robinson和Kamovsky法,以腺苷-5′-单磷酸或紐?5′-单磷酸为底物,铈为捕获剂,显示BALB/c小鼠胸腺皮质的5′-核苷酸酶。同时使用左旋咪唑抑制非特异性碱性磷酸酶活性。腺苷-5-单磷酸酶和紐?5′-单磷酸酶活性反应产物的细胞化学定位基本相似。此酶活性定位于上皮性网状细胞和某些胸腺细胞的质膜外层,特别是两者的相邻面。5′-核苷酸酶活性也见于巨噬细胞溶酶体和上皮性网状细胞的囊泡、靠近质膜的小泡及一些溶酶体内。本研究就胸腺皮质内5′-核苷酸酶的生物学意义进行了讨论。

ULTRASTRUCTURAL LOCALIZATION OF 5'-NUCLEOTIDASE IN MOUSE THYMIC CORTEX

The thymic cortex is the important site for thymocyte differentiation, maturation and selection. Direct cell-cell interactions between thymocytes and distinct stromal cells are an important pattern to demonstrate the essential role in T-cell development. In order to approach the mechanism of their interactions, ultrastructural cytochemical localization of 5'-nucleotidase activity in the thymic cortex of BALB/c mice were investigated by means of Robinson and Karnovsky method using 5'-AMP or 5'-IMP as the substrate, cerium as the capture agent, and levamisol (an inhibitor of nonspecific alkaline phosphatase) was also used. The cytochemical distribution of the reaction products from both the 5'-AMPase and 5'-IMPase activity was essentially similar. The enzyme activity was localized on the extracellular side of the plasma membrane of the epithelial reticular cells and some thymocytes, especially on their contact faces with each other. 5'-nucleotidase activity was also found in the lysosomes of macrophages and in the vacuoles, and vesicles near the plasma membrane and some lysosomes of epithelial reticular cells. The biological significance of the 5'-nucleotidase in thymic cortex was discussed.