Nakano Y, Kawamoto T, Oda K, Takano Y
Biostructural Science, Graduate School of Tokyo Medical and Dental University, Tokyo, Japan.
Connect Tissue Res. 2003;44 Suppl 1:219-22.
Net activity of tissue-nonspecific alkaline phosphatase (TNAP) and acid phosphatase (ACP) remains to be determined since enzyme histochemistry has adopted biochemically determined optimal pH, which is not likely to represent local pH in vivo. The present study aimed to evaluate TNAP and ACP activities associated with bone cells at physiological pH. At the physiological pH of tissue fluid, intense phosphatase reactions were demonstrable in osteoblasts and osteoclasts as well as the bone matrix associated with osteoclasts. In fresh-frozen and freeze-substituted specimens, intense phosphatase reactions appeared at both alkaline and neutral pH along the entire surface of osteoblasts including the osteoidal surface, where TNAP was shown to be absent by immunohistochemistry. Combined specificity tests suggested that TNAP and ACP in bone cells can serve as phosphohydrolases at pH 7.3 and that reactions along the osteoidal surface of osteoblasts differ from that of TNAP and represent novel enzyme.
由于酶组织化学采用的是生化测定的最佳pH值，而该pH值不太可能代表体内局部pH值，因此组织非特异性碱性磷酸酶（TNAP）和酸性磷酸酶（ACP）的净活性仍有待确定。本研究旨在评估生理pH值下与骨细胞相关的TNAP和ACP活性。在组织液的生理pH值下，成骨细胞、破骨细胞以及与破骨细胞相关的骨基质中都可出现强烈的磷酸酶反应。在新鲜冷冻和冷冻替代标本中，沿成骨细胞整个表面（包括类骨质表面）在碱性和中性pH值下均出现强烈的磷酸酶反应，免疫组织化学显示类骨质表面不存在TNAP。联合特异性试验表明，骨细胞中的TNAP和ACP在pH 7.3时可作为磷酸水解酶，而成骨细胞类骨质表面的反应与TNAP不同，代表一种新型酶。
