Electrical properties of extracted rat liver tissue

Abstract

We attempted to investigate the process of ischemia-induced disturbances in the rat liver, employing the electrical bio-impedance technique. The electrical bio-impedance was measured continuously over 6h by the 4-electrode method, at various incubation temperatures, in six liver samples extracted from male Wistar rats. The electrical properties of biological tissues can be expressed in terms of three parameters: extracellular resistance (Re), intracellular resistance (Ri) and cell membrane capacitance (Cm). These three parameters were calculated from the measured values of the electrical impedance by the curve-fitting technique, using a computer program. The Re value increased rapidly after the rat livers were extracted, and then decreased slowly. The Revalue reached a peak after about 13 min at 36°C, and then decreased slowly, becoming constant after 3h. There was a negative correlation between the Tmax of Re (the time when Re reached a maximum) and the incubation temperature (R=−0.973,P<0.001). The Ri value decreased once in the early stage after extraction, followed by almost no change and then an increase after 4h at 36°C. The Cm showed a similar pattern of change to the Re value, and a negative correlation was also found between the Tmax of Cm and the incubation temperature (R=−0.969,P<0.001). The increases in the Re and Cm values, and the decrease in the Ri value for quite long periods after the blood flow has stopped, suggest an increase in the resistance of extracellular fluid due to a decrease in its volume, an increase in cell membrane capacitance due to cell swelling, and a decrease in cellular fluid resistance due to an increase in its volume. The time when the Cm value decreases rapidly after an initial gradual decrease after the peak corresponds well with the time when the Ri value begins to increase, from which it is estimated that cell lysis proceeds and that the flow of extracellular fluid into the cell begins at this time. The findings of this study suggest the possibility of estimating the changes in liver tissue or the tissue structure due to ischemia.