Cultured rat hepatocytes adapt their cellular glycolytic activity and adenylate energy status to tissue oxygen tension: influences of extracellular matrix components, insulin and glucagon.
The influence of extracellular matrix components, insulin, and glucagon on the cellular response to periportal- or pericentral-equivalent tissue oxygen tension was investigated in freshly isolated rat hepatocytes cultured at 13% O2 or 4% O2 in Teflon membrane dishes. With extended culture time, significant increases in lactate release and cellular lactate content were observed in cultures at 4% O2 compared with 13% O2. This shift toward glycolysis was detectable when hepatocytes were cultured on dishes coated with rat liver crude membrane fraction (CMF/COL) but not in collagen type I-coated dishes. This indicates that extracellular matrix components are involved in the process of adaptation. ATP and total adenylate content in cells cultured at 4% O2 were up to 40% lower than in cells cultured at 13% O2. However, the adenylate energy charge was not affected, suggesting that an adequate energy supply was maintained also in hepatocytes cultured at pericentral-equivalent oxygen tension. This adaptation was reversible. When hepatocytes were transferred either from 4% to 13% O2 or from 13% to 4% O2, they adapted the corresponding metabolic profile to the new oxygen tension within 2 days. This demonstrates that hepatocytes are not fully unidirectionally programmed. The modulation of the glycolytic activity by insulin and glucagon was effective in cultures at pericentral-equivalent oxygen tension (4% O2) only. Insulin (0.1-100 nM) shifted cellular metabolism toward the glycolytic pathway and glucagon (1-100 nM) counteracted the effect of insulin in a dose-dependent manner. Clearly, oxygen tension is the principal regulator in the hepatic glycolytic activity, whereas the hormones (insulin and glucagon) act as secondary modulators.
Institute of Toxicology, Swiss Federal Institute of Technology, Schwerzenbach.
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Ohno
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Maier
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D004734:Energy Metabolism; D005109:Extracellular Matrix / Q000378:metabolism*; D005934:Glucagon / Q000378:metabolism*; D006019:Glycolysis; D007328:Insulin / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D009928:Organ Specificity; D010100:Oxygen / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D007328:Insulin; D000255:Adenosine Triphosphate; D005934:Glucagon; D010100:Oxygen