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Inhibitors of ER Ca 2+ ‐ATPase activity deplete the ATP‐ and thrombin‐sensitive Ca 2+ pool in UMR 106–01 osteosarcoma cells
Author(s) -
Meszaros Gary J.,
Karin Norman J.
Publication year - 1995
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650100506
Subject(s) - thapsigargin , intracellular , endoplasmic reticulum , calcium , chemistry , atpase , calcium atpase , plasma membrane ca2+ atpase , cytosol , compartmentalization (fire protection) , calcium in biology , inositol , endocrinology , biophysics , medicine , biochemistry , biology , enzyme , receptor , organic chemistry
While calcium release from intracellular stores is a signaling mechanism used universally by cells responding to hormones and growth factors, the compartmentalization and regulated release of calcium is cell type‐specific. We employed thapsigargin and 2,5,‐di‐( tert ‐butyl)‐1,4‐benzohydroquinone (tBuHQ), two inhibitors of endoplasmic reticulum (ER) Ca 2+ ‐ATPase activity which block the transport of Ca 2+ into intracellular stores, to characterize free Ca 2+ compartmentalization in UMR 106–01 osteoblastic osteosarcoma cells. Each drug elicited transient increases in cytosolic free Ca 2+ ([Ca 2+ ] i ), followed by a stable plateau phase which was elevated above the control [Ca 2+ ] i . The release of Ca 2+ from intracellular stores was coupled to an increased plasma membrane Ca 2+ permeability which was not due to L‐type Ca 2+ channels. Thapsigargin and tBuHQ emptied the intracellular calcium pool which was released in response to either ATP or thrombin, identifying it as the inositol 1,4,5‐trisphosphate‐sensitive calcium store. The results of sequential and simultaneous additions of thapsigargin and tBuHQ indicate that both drugs depleted the same Ca 2+ store and inhibited the same Ca 2+ ‐ATPase activity.