Mitochondrial uncoupling does not influence the stability of the intracellular signal activating plasma membrane calcium channels.
The effects of various concentrations of thapsigargin, a specific inhibitor of Ca2+-ATPase in the endoplasmic reticulum (ER) membrane, on calcium homeostasis in lymphoidal T cells (Jurkat) were investigated. Preincubation of these cells suspended in nominally calcium-free medium with 0.1 microM thapsigargin resulted in a complete release of Ca2+ from intracellular calcium stores. When the medium was supplemented with 3 mM CaCl2 the cells maintained constantly elevated level of cytosolic Ca2+. However, thapsigargin applied at lower concentration produced only a partial depletion of the stores. For example, in the cells pretreated with 1 nM thapsigargin and suspended in calcium-free medium approximately 75% of the calcium content was released from the intracellular stores. The addition of 3 mM CaCl2 to such cell suspension led to a transient increase in cytosolic calcium concentration, followed by a return to a lower steady-state. This phenomenon, related to the refilling of the ER by Ca2+, allowed to estimate the half-time for the process of cell recovery after activation of store-operated calcium channels. By this approach we have found that carbonyl cyanide m-chlorophenylhydrazone, which has been documented to inhibit calcium entry into Jurkat cells, does not influence the stability of the intracellular signal involved in the activation of store-operated calcium channels.
Zabłocki
K
K
Department of Cellular Biochemistry, Nencki Institute of Experimental Biology, Warszawa, Poland.
Makowska
A
A
Duszyński
J
J
D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D019169:Jurkat Cells; D008928:Mitochondria / Q000378:metabolism*; D011485:Protein Binding; D015398:Signal Transduction; D013050:Spectrometry, Fluorescence; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors
D015220:Calcium Channels; D004791:Enzyme Inhibitors; D019284:Thapsigargin; D002118:Calcium