Effect of 2,5-anhydro-D-mannitol on membrane potential in rat hepatocyte couplets and hepatocyte monolayer cultures.
The fructose analogue 2,5-anhydro-D-mannitol (2,5-AM), which depletes liver cells of ATP, has been shown to alter liver cell membrane potential (V(m)) in situ and in superfused liver slices. To study this effect of 2,5-AM on hepatocytes in more detail, patch-clamp experiments in the current-clamp mode were performed using two established models, rat hepatocyte couplets and confluent rat hepatocytes in primary culture. 2,5-AM, which has previously been shown to hyperpolarize hepatocytes in superfused liver slices and in vivo, failed to alter V(m) of hepatocyte couplets. Increasing intracellular Ca(2+) by addition of thapsigargin or ionomycin also did not evoke a change of V(m). This is most likely due to a lack of Ca(2+)-dependent K(+) channels in rat hepatocyte couplets. In contrast, 2,5-AM depolarized the cells in confluent hepatocyte monolayers. This depolarization was mimicked after inhibition of Na(+)/K(+) ATPase by ouabain. Ouabain was also able to block 2, 5-AM's effect on monolayer V(m). Thus, 2,5-AM affects the membrane potential of isolated and cultured hepatocytes in a way not comparable with cells integrated in the liver.
Cermak
R
R
Institute of Veterinary Physiology, University of Zürich, Winterthurerstr. 260, CH-8057, Zürich, Switzerland. cermak@vetphys.unizh.ch
Scharrer
E
E
D000818:Animals; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D015759:Ionomycin / Q000494:pharmacology; D008099:Liver / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008353:Mannitol / Q000031:analogs & derivatives* / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051381:Rats; D019284:Thapsigargin / Q000494:pharmacology
D008353:Mannitol; C031765:2,5-anhydromannitol; D015759:Ionomycin; D010042:Ouabain; D019284:Thapsigargin