Development of microdialysis probe for the kidney

被称为微透析的“生物取样”技术最初是由Ungerstedt和同事开发的。该方法的原理是从细胞外液（ECF）中提取代谢物，而不从组织中去除液体。基本器械是一种薄（直径0.65 mm）双腔探头，尖端带有半透性聚碳酸酯膜。探针用等渗盐水灌注。小分子通过简单的扩散沿着灌流液和ECF之间的浓度梯度穿过探针膜，通过包括HPLC在内的灵敏分析技术测量各种代谢物的透析液微量样品含量，因此，微透析可用于各种代谢物的ECF含量的区域性变化的时间研究。该方法最初是为脑组织研究而设计的。然而，微透析探针的直径为0.65 mm。该尺寸对于应用于以高血液流速灌注的肾脏而言相对较大。此外，由于肾脏与呼吸同步运动，因此探针的固定很困难。此外，为了观察对各种刺激的快速反应，探针需要高透析效率。因此，为了满足上述几点，我们尝试开发一种新的肾脏微透析探针。新探头的直径仅为0.2 mm，透析效率是商业探头的5 - 10倍。使用这种新开发的探针，我们已经研究了缺血和再循环过程中肾内腺苷代谢。腺苷浓度（conc.）缺血使腺苷浓度增加约2倍。然而，在用EHNA抑制腺苷脱氨酶后，在缺血期间腺苷浓度增加超过50 - 100倍。另一方面，用碘结核菌素抑制腺苷激酶后，腺苷浓度仅增加3 - 4倍。因此，从细胞中释放的腺苷

The "bio-sampling" technique called microdialysis was originally developed by Ungerstedt and colleagues. The principle of this method is to extract metabolizes from the extracellular fluid(ECF) without removal of fluid from the tissue. The basic device is a thin (0.65 mm diameter) double lumen probe with a seim-permeable polycarbonate membrane at the tip. The probe is perfused with an isotonic saline. Small molecules cross the probe membrane by simple difusion along a concetration gradient between the perfusate and the ECF.The dialysate microsample content of various metabolizes is measured by sensitive analytical techniques including HPLC.Thus, microdialysis can be used for temporal studies of regional changes in the ECF content of various metabolizes. The method was originally designed for studies in brain tissue. However, the diameter of the microdialysis probe is 0.65 mm. This size is relatively large for the application to the kidney which is perfused at high blood flow rate. Moreover, since the kidney moves in synchronicity with the respiration, the fixation of probe is difficult. In addition, to observe the rapid responses to various stimuli high dialysis efficiency will be required for probe. Thus, in order to satisfy the above points, we have tried to develop a new microdialysis probe for the kidney. The diameter of the new probe is only 0.2 mm and the dialysis efficiency is 5 - 10 times greater than the commercial probe. Using this newly developed probe we have examined the intrarenal adenosine metabolism during ischemia and recirculation. Adenosine concentration(conc.) at basal condition was around 100 nM.Ischemia increased the adenosine conc.about 2 times. However, after the inhibition of adenosine deaminase with EHNA the adenosine conc.was increased more than 50 - 100 times during ischemia. On the other hand, adenosine conc.after the inhibition of adenosine kinase with iodotubercidine increased only 3 - 4 times. Thus, the adenosine released from the ce