Verpooten G F, Nouwen E J, Hoylaerts M F, Hendrix P G, de Broe M E
Department of Nephrology-Hypertension, University of Antwerp, Edegem, Belgium.
Kidney Int. 1989 Oct;36(4):617-25. doi: 10.1038/ki.1989.238.
Specific monoclonal antibodies raised against human intestinal and human tissue-unspecific alkaline phosphatase (AP) were developed and were used to study the expression of these two isoenzymes in human renal tissue and their release into urine. Approximately 25% of the total AP content of renal tissue at the transition between cortex and medulla was of the intestinal type; the remainder was of the tissue-unspecific type (liver, bone, kidney AP). Immunoperoxidase staining using specific monoclonal antibodies against liver and intestinal AP revealed that the tissue-unspecific AP isoenzyme is present through-out the different segments of the proximal tubule, whereas intestinal-type AP is found exclusively in tubuloepithelial cells of the S3-segment of the proximal tubule. The intestinal-type enzyme obtained from the kidney had a similar heat stability and Km value, and similar immunologic and inhibitory (L-p-bromotetramisole; L-phenylalanine) characteristics compared to adult intestinal and fetal intestinal AP. Its electrophoretic mobility in agarose gel was intermediate between that of adult intestinal and fetal intestinal AP; after neuraminidase treatment it became indistinguishable from the adult intestinal isoenzyme. The intestinal-type AP found in the urine was not sensitive to neuraminidase and had a molecular weight significantly lower than the urinary tissue-unspecific AP isoenzyme. In conclusion, intestinal AP in the kidney is a specific marker for the brush border of the S3 segment of the proximal tubule, and this finding opens new perspectives in the cell biology of this particular part of the nephron.
制备了针对人肠型和人组织非特异性碱性磷酸酶（AP）的特异性单克隆抗体，并用于研究这两种同工酶在人肾组织中的表达及其向尿液中的释放。在皮质与髓质交界处，肾组织中总AP含量的约25%为肠型；其余为组织非特异性型（肝、骨、肾AP）。使用针对肝和肠AP的特异性单克隆抗体进行免疫过氧化物酶染色显示，组织非特异性AP同工酶存在于近端小管的不同节段，而肠型AP仅在近端小管S3节段的肾小管上皮细胞中发现。从肾脏获得的肠型酶与成人肠和胎儿肠AP相比，具有相似的热稳定性和Km值，以及相似的免疫和抑制（L - 对溴四咪唑；L - 苯丙氨酸）特性。其在琼脂糖凝胶中的电泳迁移率介于成人肠和胎儿肠AP之间；经神经氨酸酶处理后，它与成人肠同工酶无法区分。尿液中发现的肠型AP对神经氨酸酶不敏感，其分子量明显低于尿液中的组织非特异性AP同工酶。总之，肾脏中的肠AP是近端小管S3节段刷状缘的特异性标志物，这一发现为肾单位这一特定部分的细胞生物学开辟了新的前景。
