Measurement with microelectrodes of intracellular Na+, K+, H+ and Cl- activities and of membrane potential in normal rat liver slices and during the 4-dimethylaminoazobenzene-induced rat hepatocarcinogenesis.
Steady-state membrane potentials (Vm) and intracellular Na+ (aiNa), K+ (aiK), H+ (aiH) and Cl- (aiCl) activities were measured with double-barrelled ion-selective microelectrodes in liver slices from normal rats and during the 4-dimethylaminoazobenzene-induced (DAB) hepatocarcinogenesis. Rats fed with the experimental regimen without the carcinogen were used as control animals. In Krebs-Henseleit bicarbonate saline containing 5.5 mM glucose as bathing solution at 37 degrees C, Vm was found to be significantly lower in neoplastic hepatocytes, compared to normal liver cells. Vm decreased also in control rat liver cells. Increased Na+/K+ ratios and Na+ + K+ activities were found in cancerous hepatocytes whereas H+ and Cl- activities decreased. Therefore, the intracellular pH increased significantly in neoplastic cells, compared to normal and control cells. This could reflect activation of the Na+/H+ exchange system during the DAB-induced hepatocarcinogenesis, leading to a stimulation of cell metabolism with increased rate of protein and DNA synthesis and loss of growth control, under these conditions.
Comolli
R
R
Dipartimento di Fisiologia e Biochimica Generali Università di Milano, Italy.
Rossetti
C
C
Cremaschi
D
D
D000818:Animals; D002712:Chlorides / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D008113:Liver Neoplasms / Q000139:chemically induced* / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D008839:Microelectrodes; D011188:Potassium / Q000378:metabolism*; D011522:Protons; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*; D004124:p-Dimethylaminoazobenzene
D002712:Chlorides; D011522:Protons; D012964:Sodium; D004124:p-Dimethylaminoazobenzene; D011188:Potassium