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Volume regulatory responses in frog isolated proximal cells
Pflugers Archiv : European Journal of Physiology
|August 1, 1994
Summary
Cells regulate volume by losing solutes and water. This study found that calcium (Ca2+) and protein kinase C (PKC) signaling pathways stimulate this volume regulatory decrease (VRD) response in frog proximal tubule cells.
Area of Science:
- Cell Physiology
- Molecular Biology
- Renal Physiology
Background:
- Cells activate solute efflux pathways to restore volume after swelling.
- The intracellular signaling mechanisms for volume regulatory decrease (VRD) are not fully understood.
Purpose of the Study:
- Investigate the role of stretch-activated channels, Ca2+, and protein kinases in VRD.
- Elucidate the transduction pathways converting cell volume changes into VRD signals.
Main Methods:
- Measured cell length as an index of cell volume in isolated frog proximal tubule cells.
- Utilized a photodiode array for continuous cell length measurement.
- Applied various inhibitors and activators, including Ba2+, Gd3+, DIDS, Ca2+ removal, phorbol esters (PMA, PDC), staurosporine, and IBMX.
Main Results:
- VRD was observed in about 50% of cells and inhibited by Ba2+, Gd3+, DIDS, and Ca2+ removal.
- The active phorbol ester PMA and a phosphatase inhibitor accelerated VRD.
- VRD was prolonged by an inactive phorbol ester (PDC) and inhibited by PMA, Gd3+, Ca2+-free conditions, and staurosporine.
Conclusions:
- Ca2+ and protein kinase C (PKC) play a stimulatory role in VRD.
- Protein phosphorylation mediated by Ca2+ and PKC is crucial for VRD.
- These findings shed light on the signaling pathways governing cell volume regulation.