Transmembrane potential of isolated rat alveolar type II cells.
Castranova-V; Jones-GS; Miles-PR
J Appl Physiol: Respir Environ Exercise Physiol 1983 Jun; 54(6):1511-1517
The resting transmembrane potential (Em) of isolated alveolar type- II cells from male Sprague-Dawley-rats was investigated along with the factors which alter this potential. The fluorescent probe, Di-S- C3, was used to determine the Em of the cells. Fluorescence decreased as Em became more negative (hyperpolarization) and increased as Em became more positive (depolarization). At rest the Em was about -27 millivolts (mV) and was dependent on the extracellular potassium concentration, indicating the membrane depolarized as external potassium increased. The cellular preparation in this study contained 85 percent type-II cells with the major contaminating cells being alveolar macrophages and leukocytes, each representing less than 5 percent of the cellular sample. After correcting for this contamination, the estimate of Em was -24mV for type-II cells. The sodium/potassium pump contributed to the electronegativity of the resting Em. Type-II cells were more permeable to potassium than to sodium. A ouabain induced depolarization seemed to result from inhibition of an actual electrogenic sodium/potassium pump. Phorbol-myristate-acetate (PMA) induced sodium dependent membrane depolarization, an increase in the fluorescence of Di-Si-C3. PMA caused a 43 percent increase in oxygen consumption but this was not due to cellular contamination. The authors suggest that it may be possible that sodium dependent depolarization triggers the proliferation of type-II cells occurring after oxidant injury to the lungs.
NIOSH-Author; Lung-cells; Laboratory-animals; In-vitro-studies; Alveolar-cells; Cell-cultures; Lung-tissue;
Author Keywords: membrane potential; electrogenic pump; ouabain; Di-S-C3(5); phorbol myristate acetate; oxygen consumption
Journal of Applied Physiology: Respiratory, Environmental and Exercise Physiology