Highly cooperative Ca2+ elevations in response to Ins(1,4,5)P3 microperfusion through a patch-clamp pipette
| Autor: | Daniel Pablo Lew, G. W. Mayr, Nicolas Demaurex, C. van Delden, Karl-Heinz Krause, Michelangelo Foti, Jean Jacquet, Jacques Schrenzel |
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| Rok vydání: | 1995 |
| Předmět: |
Calcium/ metabolism
Cell Membrane Permeability Patch-Clamp Techniques Time Factors Fura-2 Kinetics Biophysics Analytical chemistry HL-60 Cells Cooperativity Inositol 1 4 5-Trisphosphate 03 medical and health sciences symbols.namesake chemistry.chemical_compound 0302 clinical medicine Subcellular Fractions/metabolism Negative feedback Perfusion/methods Extracellular Humans Patch clamp Fluorescent Dyes 030304 developmental biology ddc:616 0303 health sciences Hill differential equation Cell Membrane/metabolism Calcium Radioisotopes Microchemistry Cell Membrane Models Theoretical Microfluorimetry Perfusion chemistry symbols Calcium Mathematics 030217 neurology & neurosurgery Inositol 1 4 5-Trisphosphate/administration & dosage/metabolism/ pharmacology Research Article Subcellular Fractions |
| Zdroj: | Biophysical Journal, Vol. 69, No 6 (1995) pp. 2378-2391 |
| ISSN: | 0006-3495 |
| Popis: | To study the initial kinetics of Ins(1,4,5)P3-induced [Ca2+]i elevations with a high time resolution and to avoid the problem of cell-to-cell heterogeneity, we have used the combined patch-clamp/microfluorimetry technique. The mathematical description of the microperfusion of Ins(1,4,5)P3 and the subsequent Ca2+ release consists of a monoexponential decay (cytosolic Ins(1,4,5)P3 concentration) and a Hill equation (Ins(1,4,5)P3 dose-response curve). Two additional Hill equations and an integration were necessary to include a putative dependence of Ins(1,4,5)P3-induced Ca2+ release on [Ca2+]i. Best-fitting analysis assuming [Ca2+]i-independent Ca2+ release yielded Hill coefficients between 4 and 12. The high cooperativity was also observed with the poorly metabolizable analog Ins(2,4,5)P3 and was independent of extracellular [Ca2+]. Best-fitting analysis including a positive [Ca2+]i feedback suggested a cooperativity on the level of Ins(1,4,5)P3-induced channel opening (n = 2) and an enhancement of Ins(1,4,5)P3-induced Ca2+ release by [Ca2+]i. In summary, the onset kinetics of Ins(1,4,5)P3-induced [Ca2+]i elevations in single HL-60 granulocytes showed a very high cooperativity, presumably because of a cooperativity on the level of channel opening and a positive Ca2+ feedback, but not because of Ca2+ influx or Ins(1,4,5)P3 metabolism. This high cooperativity, acting in concert with negative feedback mechanisms, might play an important role in the fine-tuning of the cellular Ca2+ signal. |
| Databáze: | OpenAIRE |
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