Changes in electrical resistivity of swine liver after occlusion and postmortem

Abstract

The resistivity of swine liver tissue was measured in vivo, during induced ischaemia and post-mortem, so that associated changes in resistivity could be quantified. Plunge electrodes, the four-terminal method and a computer-automated measurement system were used to acquire resistivities between 10 Hz and 1 MHz. Liver resistivity was measured in vivo in three animals at 11 locations. At 10 Hz, resistivity was 758±170 Ω·cm. At 1 MHz, the resistivity was 250±40Ω·cm. The resistivity time course was measured during the first 10 min after the liver blood supply in one animal had been occluded. Resistivity increased steadily during occlusion. The change in resistivity of an excised tissue sample was measured during the first 12h after excision in one animal. Resistivity increased during the first 2h by 53% at 10 Hz and by 32% at 1MHz. After 2h, resistivity decreased, probably owing to membrane breakdown. The resistivity data were fitted to a Cole-Cole circle, from which extracellular resistance R_e, intracellular resistance R_i and cell membrane capacitance C_m were estimated. R_e increased during the first 2h by 95% and then decreased, suggesting an increase in extracellular volume. C_m increased during the first 4h by 40%, possibly owing to closure of membrane channels, and then decreased, suggesting membrane breakdown. R_i stayed constant during the initial 6h and then increased.