Control of biliary phospholipid secretion. Effect of continuous and discontinuous infusion of taurocholate on biliary phospholipid secretion.
A major determinant of biliary lipid secretion is bile-salt secretion. Taurocholate (TC), a micelle-forming bile salt, was infused continuously at different rates in both isolated perfused livers and biliary-fistula rats. In both of these systems, infusion of TC brought about an elevated secretion of phosphatidylcholine for the duration of the TC infusion period. Initial phospholipid/bile-salt ratios in the bile were higher in the whole-animal model than in isolated livers, but at the higher infusion rates both secreted approx. 6 mol of phospholipid for every 100 mol of bile salt. The secretion of phospholipid, which was maintained even at high rates of bile-salt infusion, suggest a continuous and regulated phospholipid supply and secretion mechanism. In contrast, however, multiple short pulses of TC to the perfused liver, which brought about relatively equal biliary bile-salt output pulses, did not bring about equal phospholipid outputs, since the phospholipid peak size declined with each bile-salt pulse. These experiments taken together suggest either that a threshold (intracellular) bile-salt concentration may be required to 'switch-on' the phospholipid supply and that it may need to be maintained for continuous biliary phospholipid supply to the canalicular membrane.
D000818:Animals; D001646:Bile / Q000187:drug effects / Q000378:metabolism*; D001647:Bile Acids and Salts / Q000378:metabolism; D001658:Biliary Fistula / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D010477:Perfusion; D010743:Phospholipids / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013656:Taurocholic Acid / Q000494:pharmacology*
D001647:Bile Acids and Salts; D010743:Phospholipids; D013656:Taurocholic Acid