Delayed activation of calcium pump during transient increases in cellular Ca2+ concentration and K+ conductance in hyperpolarizing human red cells
| Autor: | Birthe Foder, Ole Scharff |
|---|---|
| Rok vydání: | 1986 |
| Předmět: |
Erythrocytes
Calmodulin Protonophore Calcium pump Potassium Biophysics Analytical chemistry Ionophore chemistry.chemical_element Calcium Biochemistry Ion Channels Extracellular Humans Ion transporter Calcimycin biology Chemistry Biological Transport Cell Biology Cobalt Hydrogen-Ion Concentration biology.protein |
| Zdroj: | Biochimica et biophysica acta. 861(3) |
| ISSN: | 0006-3002 |
| Popis: | The net Ca 2+ influx was increased in human red cells in suspension by adding moderate concentrations of the Ca 2+ ionophore A23187, and due to the increased cellular Ca 2+ concentration ([Ca] i ) the K + channels opened (the ‘Gardos effect’). At low K + concentration and with the protonophore CCCP in the buffer-free medium the cells hyperpolarized and the extracellular pH (pH 0 ) increased, enhancing the A23187-mediated net Ca 2+ influx. This elicited a prolonged response, viz. a primary transient increase of pH 0 and [Ca] i followed by one or more spontaneous pH 0 and [Ca] i transients. We explored the pump-mediated Ca 2+ efflux by blocking the A23187-mediated Ca 2+ flux with CoCl 2 at appropriate times during the prolonged response. The Ca 2+ pumping was higher during the descendent than during the ascendent phase of the primary transient at equal values of [Ca] i . The data were anlyzed using a mathematical model that accounts for the prolonged oscillatory response, including pH 0 and [Ca] i . In conclusion, the activation of the Ca 2+ pump is delayed due to slow binding of cellular calmodulin, which is a hysteretic response to a rapid increase of the cellular Ca 2+ concentration. This mechanism may be important for generation and execution of transient signals in other types of cell. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|