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[Ca2+]i oscillations and [Ca2+]i waves in rat megakaryocytes
1Department of Physiology, University of Connecticut Health Center, Farmington 06030-3505, USA.
Cell Calcium
|May 1, 1997
Summary
Adenosine triphosphate (ATP) triggers calcium (Ca2+) oscillations in rat megakaryocytes. Cyclic nucleotides like cAMP and cGMP inhibit these oscillations, which propagate as calcium waves.
Area of Science:
- Cellular Biology
- Physiology
- Biochemistry
Background:
- Megakaryocytes are crucial for platelet production.
- Intracellular calcium (Ca2+) signaling plays a vital role in cell function.
- ATP is a known signaling molecule in various cell types.
Purpose of the Study:
- To investigate ATP-induced intracellular calcium ([Ca2+]i) oscillations in rat megakaryocytes.
- To explore the effects of cyclic nucleotides (cGMP and cAMP) on these oscillations.
- To characterize the propagation dynamics of [Ca2+]i waves.
Main Methods:
- Fluorescence ratio microscopy was used to measure [Ca2+]i in single rat megakaryocytes.
- Video rate fluorescence ratio imaging was employed to analyze [Ca2+]i wave propagation.
- Temperature dependence studies were conducted to elucidate wave dynamics.
Main Results:
- ATP induced [Ca2+]i oscillations with cell-to-cell variability in peak [Ca2+]i, frequency, and duration.
- Agents increasing intracellular cGMP or cAMP levels inhibited these [Ca2+]i oscillations.
- Agonist-induced [Ca2+]i oscillations resulted from [Ca2+]i waves spreading at ~35 microns/s.
- Calcium decay during oscillations was temperature-dependent, while rise was not, suggesting diffusion-limited propagation.
Conclusions:
- Rat megakaryocyte [Ca2+]i oscillations are sensitive to ATP concentration and intracellular calcium buffering.
- Cyclic GMP and cyclic AMP signaling pathways modulate ATP-induced calcium oscillations.
- Calcium wave propagation in megakaryocytes is primarily limited by calcium diffusion.