title: Ion microscopy evidence that La3+ releases Ca2+ from Golgi complex in LLC-PK1 cells.
abstract: The effect of La3+ on LLC-PK1 cells was investigated by ion microscopy, a mass spectrometry-based technique with a spatial resolution of approximately 0.5 micron. Cells were incubated with LaCl3 for 10 min. (1 mM) or 30 min (0.1 mM), and intracellular calcium distributions were measured with a Cameca IMS-3f ion microscope in cryogenically prepared cells. Compared with control cells, La3+ reduced total calcium in the Golgi complex by > 100 microM in both treatments, whereas other cellular regions, such as the nucleus and cytoplasm, remained largely unchanged. These two treatments were repeated on cells that were preincubated with 1 mM ouabain. The presence of ouabain in the medium increased the loss of calcium from the Golgi by about fourfold compared with the treatments without ouabain. The La3+ effect, therefore, was amplified by ouabain-induced Na+ loading, indicating a possible involvement of a Na+/La3+ exchanger. La3+ was detected within cells and its influx was facilitated by Na+ loading. These results suggest that La3+ may affect cellular calcium homeostasis by actions other than as a simple Ca2+ antagonist.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D018374:LLC-PK1 Cells; D007811:Lanthanum / Q000494:pharmacology*; D018613:Microscopy, Confocal; D010042:Ouabain / Q000494:pharmacology; D019831:Sodium-Calcium Exchanger; D018629:Spectrometry, Mass, Secondary Ion; D013552:Swine
chemical_list: D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D010042:Ouabain; D007811:Lanthanum; D002118:Calcium