We investigated the molecular mechanism underlying the progressive loss of Na(+)-dependent bile salt uptake in primary cultured rat hepatocytes. A specific cDNA probe was used to quantitate the levels of mRNA encoding the Na(+)-taurocholate-cotransporting polypeptide at various culture times. Hepatocytes were cultured on collagen in the presence of insulin (10(-7) mol/L), dexamethasone (10(-7) mol/L) and 10% fetal calf serum for up to 72 hr. During this time period the dissociation constant of Na(+)-dependent taurocholate uptake remained stable (19 to 39 mumol/L), whereas the maximum velocity values decreased from 100% at 3 hr to 55%, 22% and 4% at 24, 48 and 72 hr, respectively. Concomitantly the levels of the Na(+)-taurocholate-cotransporting polypeptide mRNA also decreased from 100% at 3 hr to 41%, 24% and 4% at the later time points. In contrast, Northern hybridization with complementary DNA probes for three common housekeeping gene products revealed a 1.8- to 3.4-fold increase in the levels of mRNA encoding the alpha-subunit of the Na+K(+)-ATPase, beta-actin and glycerol-3-phosphate dehydrogenase. These data indicate that the loss of Na(+)-dependent bile salt uptake in primary cultures of rat hepatocytes is caused by decreased levels of its specific mRNA. Hence the studies further confirm that without specific measures (primary) cultured rat hepatocytes reverse their liver-specific phenotype to a more fetal pattern of gene expression.
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Molecules
January 2025
Department of Medical Biosciences, Faculty of Life Sciences, Ritsumeikan University, Kusatsu 525-8577, Shiga, Japan.
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Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.
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Biomembrane Group, Tokyo Metropolitan Institute of Medical Science, 6-1-2, Kamikitazawa, Setagaya-Ku, Tokyo 113-8613, Japan.
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Free University of Berlin, Institute of Pharmacy, Pharmacology and Toxicology, Berlin, Germany; BASF SE, Experimental Toxicology and Ecology, Ludwigshafen am Rhein, Germany.
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Department of Pharmacognosy, Goa College of Pharmacy, Panaji, Goa, 403 001, India. Electronic address:
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