A possible rate limiting factor in urea synthesis by isolated hepatocytes: the transport of ornithine into hepatocytes and mitochondria.
The uptake of ornithine by isolated hepatocytes and by the particulate fraction of these cells was measured under various conditions of urea synthesis. Under conditions of maximum urea synthesis, i.e. in the presence of glucose, ornithine, ammonium chloride and oleate, the cytosolic concentration and the mitochondrial concentration of ornithine was extremely low, while citrulline accumulated in the cytosol. The data indicate that the rate of citrulline synthesis is limited by the availability of mitochondrial ornithine.
D000818:Animals; D001692:Biological Transport; D002956:Citrulline / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism*; D009952:Ornithine / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014508:Urea / Q000096:biosynthesis*
D002956:Citrulline; D014508:Urea; D009952:Ornithine