Mandel L J, Takano T, Soltoff S P, Murdaugh S
Machu Picchu Research Foundation, Duke University Medical Center, Durham, North Carolina 27710.
J Clin Invest. 1988 Apr;81(4):1255-64. doi: 10.1172/JCI113443.
When a suspension of rabbit proximal tubules is subjected to anoxia, ATP falls by 80-90% during 40 min of anoxia, and upon reoxygenation (reox) the cells only recover 25-50% of their initial ATP. Addition of Mg-ATP (magnesium chloride-treated ATP), Mg-ADP, or Mg-AMP (five aliquots of 200 nmol/ml added 10 min apart) during anoxia causes complete recovery of ATP levels, and respiratory and transport function after 40 min of reox. Similar additions of adenosine (ADO), or inosine (INO), or Mg-ATP only during reox are less effective. Lactate dehydrogenase (LDH) release after 40 min of anoxia is 30-40% under control conditions, only 10-15% when adenine nucleotides or ADO are added during anoxia, and 20% when INO is added, suggesting that these additions may stabilize the plasma membrane during anoxia and help preserve cellular integrity. During reox, recovery may depend on the entry of ATP precursors and, therefore, we explored the mechanism whereby exogenous ATP increases the intracellular ATP content. Additions of Mg-ATP, Mg-ADP, or Mg-AMP to continuously oxygenated tubules increase cellular ATP content three- to fourfold in 1 h. The added ATP and ADP are rapidly degraded to AMP, and more slowly to ADO, INO, and hypoxanthine. Furthermore, the ATP-induced increase in cellular ATP is abolished by the exogenous addition of adenosine deaminase, which converts extracellular ADO to INO. These results suggest that the increase in cellular ATP requires extracellular ADO. The ADO obtained from the breakdown of AMP may be preferentially transported into the renal cells to be resynthesized into cellular AMP and ATP.
当兔近端肾小管悬浮液处于缺氧状态时，在40分钟的缺氧过程中，三磷酸腺苷（ATP）含量下降80 - 90%，再给氧（复氧）时，细胞仅能恢复其初始ATP含量的25 - 50%。在缺氧期间添加氯化镁处理的ATP（Mg - ATP）、Mg - ADP或Mg - AMP（每隔10分钟添加5份200 nmol/ml）可使ATP水平完全恢复，并在复氧40分钟后恢复呼吸和转运功能。仅在复氧期间类似地添加腺苷（ADO）、肌苷（INO）或Mg - ATP效果较差。在对照条件下，缺氧40分钟后乳酸脱氢酶（LDH）释放率为30 - 40%，在缺氧期间添加腺嘌呤核苷酸或ADO时仅为10 - 15%，添加INO时为20%，这表明这些添加物可能在缺氧期间稳定质膜并有助于保持细胞完整性。在复氧期间，恢复可能取决于ATP前体的进入，因此，我们探讨了外源性ATP增加细胞内ATP含量的机制。向持续供氧的肾小管中添加Mg - ATP、Mg - ADP或Mg - AMP可使细胞ATP含量在1小时内增加三到四倍。添加的ATP和ADP迅速降解为AMP，然后更缓慢地降解为ADO、INO和次黄嘌呤。此外，外源性添加腺苷脱氨酶可消除ATP诱导的细胞ATP增加，腺苷脱氨酶可将细胞外ADO转化为INO。这些结果表明，细胞ATP的增加需要细胞外ADO。由AMP分解产生的ADO可能优先转运到肾细胞中重新合成细胞内AMP和ATP。
