title: Effects of lysophospholipids on Ca2+ transport in rat liver mitochondria incubated at physiological Ca2+ concentrations in the presence of Mg2+, phosphate and ATP at 37 degrees C.
abstract: Lysophospholipids caused the release of 45Ca2+ from isolated rat liver mitochondria incubated at 37 degrees C in the presence of low concentrations of free Ca2+, ATP, Mg2+, and phosphate ions. The concentrations of lysophosphatidylethanolamine, lysophosphatidylcholine, lysophosphatidic acid and lysophosphatidylinositol which gave half-maximal effects were 5, 26, 40 and 56 microM, respectively. The effects of lysophosphatidylethanolamine were not associated with a significant impairment of the integrity of the mitochondria as monitored by measurement of membrane potential and the rate of respiration. Lysophosphatidylethanolamine did not induce the release of Ca2+ from a microsomal fraction, or enhance Ca2+ inflow across the plasma membrane of intact cells, but did release Ca2+ from an homogenate prepared from isolated hepatocytes and incubated under the same conditions as isolated mitochondria. The proportion of mitochondrial 45Ca2+ released by lysophosphatidylethanolamine was not markedly affected by altering the total amount of Ca2+ in the mitochondria, the concentration of extramitochondrial Mg2+, by the addition of Ruthenium Red, or when oleoyl lysophosphatidylethanolamine was employed instead of the palmitoyl derivative. The effects of 5 microM-lysophosphatidylethanolamine were reversed by washing the mitochondria. The possibility that lysophosphatidylethanolamine acts to release Ca2+ from mitochondria in intact hepatocytes following the binding of Ca2+-dependent hormones to the plasma membrane is briefly discussed.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D066298:In Vitro Techniques; D008099:Liver / Q000166:cytology / Q000378:metabolism; D008246:Lysophospholipids; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D010710:Phosphates / Q000494:pharmacology*; D010743:Phospholipids / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D008246:Lysophospholipids; D010710:Phosphates; D010743:Phospholipids; D000255:Adenosine Triphosphate; D008274:Magnesium; D002118:Calcium