Calcium-pH Crosstalks in the human mast cell line HMC-1: Intracellular alkalinization activates calcium extrusion through the plasma membrane Ca2+-ATPase
✍ Scribed by Octavio Pernas-Sueiras; Amparo Alfonso; Mercedes R. Vieytes; Alberto Orfao; Luis Escribano; Sánchez-Jiménez Francisca; Luis M. Botana
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 234 KB
- Volume
- 99
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
Abstract
The human mast cell line (HMC‐1) has been used to study the relationship between intracellular pH and cytosolic calcium (Ca^2+^) in mast cells. Thapsigargin (TG) caused store‐operated Ca^2+^ entry, that is enhanced by the PKC activator PMA. NH~4~Cl‐induced alkalinization showed an inhibitory effect on TG‐sensitive stores depletion (not on TG‐insensitive stores), and also on final cytosolic Ca^2+^ levels reached in response to both TG and the ionophore ionomycin. Loperamide, a positive modulator of store‐operated channels, induced a slight Ca^2+^ entry by itself, and also increased TG‐induced Ca^2+^ entry. This enhancement was not enough to reverse the inhibitory effect of NH~4~Cl‐induced alkalinization. When comparing the effect of NH~4~Cl‐induced alkalinization on Ca^2+^ levels, with those observed using Ca^2+^ channel blockers (namely Ni^2+^ and SKF‐96365), cytosolic profiles for this ion are different, either in modified saline solution or in HCO‐free medium. Thus, it seems unlikely that the inhibitory effect of NH~4~Cl‐induced alkalinization on Ca^2+^ is taking place by blockage of Ca^2+^ entry. Furthermore, inhibition of the plasma membrane Ca^2+^‐ATPase (an important mechanism for Ca^2+^ efflux) with sodium orthovanadate (SO) matches with the inhibition of the negative effect on Ca^2+^ levels elicited by NH~4~Cl. Data indicate that NH~4~Cl‐induced alkalinization might be activating Ca^2+^ efflux from the cell, by stimulation of the plasma membrane Ca^2+^‐ATPase, and also confirm our previous finding that Ca^2+^ is a secondary signal to activate HMC‐1 cells. J. Cell. Biochem. 99: 1397–1408, 2006. © 2006 Wiley‐Liss, Inc.