title: Transport of calcium ions by Ehrlich ascites-tumour cells.
abstract: Ehrlich ascites-tumour cells accumulate Ca2+ when incubated aerobically with succinate, phosphate and rotenone, as revealed by isotopic and atomic-absorption measurements. Ca2+ does not stimulate oxygen consumption by carefully prepared Ehrlich cells, but des so when the cells are placed in a hypo-osmotic medium. Neither glutamate nor malate support Ca2+ uptake in 'intact' Ehrlich cells, nor does the endogenous NAD-linked respiration. Ca2+ uptake is completely dependent on mitochondrial energy-coupling mechansims. It was an unexpected finding that maximal Ca2+ uptake supported by succinate requires rotenone, which blocks oxidation of enogenous NAD-linked substrates. Phosphate functions as co-anion for entry of Ca2+. Ca2+ uptake is also supported by extra-cellular ATP; no other nucleoside 5'-di- or tri-phosphate was active. The accumulation of Ca2+ apparently takes place in the mitochondria, since oligomycin and atractyloside inhibit ATP-supported Ca2+ uptake. Glycolysis does not support Ca2+ uptake. Neither free mitochondria released from disrupted cells nor permeability-damaged cells capable of absorbing Trypan Blue were responsible for any large fraction of the total observed energy-coupled Ca2+ uptake. The observations reported also indicate that electron flow through energy-conserving site 1 promotes Ca2+ release from Ehrlich cells and that extra-cellular ATP increase permeability of the cell membrane, allowing both ATP and Ca2+ to enter the cells more readily.
mesh_terms: D000255:Adenosine Triphosphate / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D001278:Atractyloside / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D002458:Cell Fractionation; D002460:Cell Line; D008274:Magnesium / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism; D009840:Oligomycins / Q000494:pharmacology; D009994:Osmolar Concentration; D010101:Oxygen Consumption / Q000187:drug effects; D010710:Phosphates / Q000378:metabolism; D012402:Rotenone / Q000494:pharmacology; D013386:Succinates / Q000378:metabolism; D014343:Trypan Blue / Q000378:metabolism
chemical_list: D009840:Oligomycins; D010710:Phosphates; D013386:Succinates; D012402:Rotenone; D001278:Atractyloside; D000255:Adenosine Triphosphate; D014343:Trypan Blue; D008274:Magnesium; D002118:Calcium