Oxygen availability regulates metabolism and gene expression in trout hepatocyte cultures.
We studied the metabolic rate, cellular energetic state, hypoxia-inducible factor-1 (HIF-1) activation, and expression of enzymes involved in energy metabolism using rainbow trout (Oncorhynchus mykiss) hepatocytes over the oxygen range from 21 to 1 kPa. Oxygen dependence of these factors was assessed by gradually reducing oxygen supply to cells from 21 kPa to 10, 5, 2, and 1 kPa. Moreover, time course experiments for up to 20 h at oxygen tensions of 1 and 2 kPa were carried out. Reduction of oxygen from 21 kPa to 10, 5, 2, and 1 kPa decreased metabolic rate of the cells by 14, 24, 37, and 46%, respectively. This response was instantaneous and fully reversible upon reoxygenation. Cellular ATP content and the expression of all mRNAs studied decreased when oxygen was reduced from 21 to 5 and 2 kPa. The lowest ATP levels, approximately 43% of the initial value, were measured at 5 kPa of oxygen, whereas the reduction in mRNA amounts was most pronounced at 2 kPa. At 1 kPa oxygen tension, both ATP content and mRNA amounts returned to normoxic (21 kPa) levels with a concomitant activation of HIF-1, indicating reorganization of energy metabolism in adaptation of cells to low oxygen supply. These results show that oxygen has a direct regulatory effect on metabolism of trout hepatocyte cultures, supporting the view that oxygen has a profound role in metabolic regulation in cells.
Rissanen
Eeva
E
Centre of Excellence in Evolutionary Genetics and Physiology, Dept. of Biology, Univ. of Turku, FIN-20014, Turku, Finland. eeva.rissanen@utu.fi
Tranberg
Hanna K
HK
Nikinmaa
Mikko
M
D000199:Actins / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001481:Basal Metabolism / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D004734:Energy Metabolism / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology*; D005941:Glucokinase / Q000235:genetics / Q000378:metabolism; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D051793:Hypoxia-Inducible Factor 1 / Q000235:genetics / Q000378:metabolism; D008660:Metabolism / Q000502:physiology*; D017686:Oncorhynchus mykiss / Q000235:genetics / Q000502:physiology; D010100:Oxygen / Q000502:physiology*; D011770:Pyruvate Kinase / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
D000199:Actins; D051793:Hypoxia-Inducible Factor 1; D012333:RNA, Messenger; D000255:Adenosine Triphosphate; D005941:Glucokinase; D011770:Pyruvate Kinase; D010100:Oxygen