Development of Micro-Probe for Continuous Sampling of Interstitial Fluid in Myocardium for Evaluation of Physiological Circulation, Control, and Mass Transport.

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We measured the hydraulic permeability and separation characteristics of polyethersulfone membranes before and after adsorption and deposition of plasma proteins and then performed quantitative analysis of membrane performance. The hydraulic permeability of a membrane of 100,000 molecular weight cut off (MWCO) declined 20 to 30% after adsorption of bovine serum albumin. The observed sieving coefficient, which is the ratio of filtrate to bulk concentrations, of polydisperse dextran through a 30,000 MWCO membrane decreased up to 50% after albumin adsorption.According to the above results, the effects of plasma protein adsorption and deposition on membrane separation performance were significant, and it is crucial for quantitative microdialy methodology to make precise evaluation of recovery rate and % recovery before, during and after microdialysis.In the second year, we attempted to recover bioactive compounds from some organs such as kidney and heart using a 20,000 MWCO polycarbonate microdialysis probe. In our preliminary experiments, % recovery of adenosine was about 15%, and one of angiotensin II was about 7%. We successfully recovered angiotensin II of the order of ppm from a canine kidney. However, some change in membrane performance seemingly due to protein adsorption was observed, and thus, some pretreatment and/or other membrane materials may need to be considered. In another preliminary experiments of a rat heart using a Langendorff perfusion system, the perfusate from the pulmonary artery was collected, and concentrations of adenosine, inosine, and hypoxanthine were measured using a high performance liquid chromatography. We confirmed continuous monitoring of enhanced production of adenosine and its metabolites during ischemia. We are currently attempting to collect a regional myocardial fluid, especially ATP metabolites using a microdialysis technique.