Regulation of D-beta-hydroxybutyrate dehydrogenase in rat hepatoma cell lines.
Quantitation of D-beta-hydroxybutyrate dehydrogenase (BDH) in normal rat hepatocytes was compared with that in two rat hepatoma cell lines, H4-II-EC3 and RLT-3C. BDH activity in normal rat hepatocyte mitochondria was 321 nmol/min/mg, which was greatly reduced to 10.7 nmol/min/mg and 1.7 nmol/min/mg in H4-II-EC3 and RLT-3C cell mitochondria, respectively. The cell growth rate and L-[35S]methionine incorporation rate showed that RLT-3C cells had the highest growth rate (32.4-h doubling time) and the fastest protein biosynthesis rate (2.65 x 10(5) cpm/min/10(6) cells). The H4-II-EC3 cell line grew more slowly (48.5-h doubling time) and had lower protein biosynthesis rate (1.46 x 10(5) cpm/min/10(6) cells). The protein synthesis rate in hepatocytes was 1.25 x 10(5) cpm/min/10(6) cells. These results suggest that there is a reciprocal correlation between BDH activity and cell growth and protein synthesis rates. Immunochemical quantitation of BDH showed the amount of BDH in H4-II-EC3 and RLT-3C cells was about 4.8 and 0.5% of that in normal rat hepatocytes, respectively. Quantitation of BDH by biosynthesis indicated that BDH content in H4-II-EC3 cells and RLT-3C cells was 9.3 and 4.0% of that of normal hepatocytes, respectively. Precursor BDH synthesized by in vitro translation primed with RNA of H4-II-EC3 cells or RLT-3C cells was 3.0 and 1.1% of that translated from normal rat hepatocyte RNA. These results suggest that the decrease in BDH content in hepatoma cells results from a decrease in functional BDH-mRNA. The coupling of a decrease in BDH activity with an increase in activity of succinyl-CoA: acetoacetyl-CoA transferase in hepatoma cells may play a role in generating additional energy required for the rapid growth of tumor cells.
Zhang
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WW
Department of Biology, University of Alabama, Tuscaloosa 35487-0344.
Churchill
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Lindahl
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Churchill
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D000818:Animals; D002455:Cell Division; D015256:Coenzyme A-Transferases / Q000032:analysis; D006884:Hydroxybutyrate Dehydrogenase / Q000032:analysis* / Q000096:biosynthesis / Q000235:genetics; D008114:Liver Neoplasms, Experimental / Q000201:enzymology* / Q000473:pathology; D008930:Mitochondria, Liver / Q000201:enzymology; D009363:Neoplasm Proteins / Q000096:biosynthesis; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D014407:Tumor Cells, Cultured
D009363:Neoplasm Proteins; D012333:RNA, Messenger; D006884:Hydroxybutyrate Dehydrogenase; D015256:Coenzyme A-Transferases