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 Omega(.)cm. At 1 MHz, the resistivity was 250 +/- 40 Omega(.)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 12 h after excision in one animal. Resistivity increased during the first 2 h by 53% at 10 Hz and by 32% at 1 MHz. After 2 h, 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 2 h by 95% and then decreased, suggesting an increase in extracellular volume. C-m increased during the first 4 h by 40%, possibly owing to closure of membrane channels, and then decreased, suggesting membrane breakdown. R-i stayed constant during the initial 6 h and then increased.