Kidneys microdialysis

While both of these devices use hollow fiber membranes similar to the primary components of kidney dialyzer units, the difference between the two techniques lies in how the analyte undergoes mass transport into the device. Microdialysis sampling is a diffusion-based separation process that requires the analyte to freely diffuse from the tissue space into the membrane inner lumen in order to be collected by the perfusion fluid that passes through the inner lumen of the fiber. Ultrafiltration pulls sample fluid into the fiber lumen by applying a vacuum to the membrane (Figure 6.1). 

The availability of membranes of very small cylindrical size, the so-called hollow fibres used in artificial kidney cartridges, thus provided a great impulse to the development of this technique, and much of the original research work was done by Ungerstedt. He implanted hollow fibres into rat brains in order to mimic the function of blood vessels [4] since then, this simple microdialysis probe has been markedly improved [5-8]. A vast number of different designs have appeared [9-14] resulting in probes that, because of their narrow cylindrical shape, can be handled like a needle and easily implanted into brain and many other tissues. 

Figure 12 Typical microdialysis probes for various tissues of rats or similar-size animals. (A) intracerebral guide cannula and rigid concentric cannula probe for brain tissue, (B) linear probe used for sampling peripheral tissues such as liver, muscle, dermis, tumor, kidney, (C) vascular probe for sampling from the jugular vein, and (D) shunt probe for sampling from the bile duct. Unlabeled arrows indicate direction of dialysate flow into and out of probes. (Courtesy of Bioanalytical Systems Inc.)...

Microdialysis is used to collect solutes present in the extracellular fluid via a microdialysis probe with a semipermeable membrane at its tip (see Fig. 14.8). The probe is perfused by a buffer (perfusate), and solutes from the environment surrounding the probe diffuse though the membrane into the perfused solution. Perfusate with the solutes (dialysate) is then collected for ex situ analysis. Microdialysis has been used in vivo to monitor the local concentrations of solutes in the extracellular fluids in a number of different tissues. The first microdialysis experiments were conducted on the brain and blood plasma (Bito et al., 1966). It has since been used to study metabolism in numerous tissues such as brain, muscles, tendons, subcutaneous adipose tissue, lungs, kidneys, and liver (Flock and Kloft, 2005 de la Pena et al., 2000 Jackson, 2005 Siddiqui and Shuaib, 2001). Microdialysis is widely used for pharmacokinetic research (Davies, 1999 de Lange et al., 2000 Verbeeck, 2000) and has also been used to monitor cell metabolites in cell culture medium (Wu et al., 2001). 

Saito, A., Suzuki, H., Bomsztyk, K., and Ahmad, S. (1998). Regeneration of peritoneal effluent by Madin-Darby canine kidney ceUs-lined hollow fibers. Mater. Sci. Eng. C 6(4), 221-226. Scheller, D., and Kolb, J. (1991). The internal reference technique in microdialysis A practical approach to monitoring dialysis efficiency and to calculating tissue concentration from dialysate samples. J. Neurosci. Methods 40(1), 31-38. 

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