Intracellular Ca2+ sequestration in cultured mouse fibroblasts: ATP-dependent Ca2+ uptake by saponin-permeabilized Swiss 3T3 cells
✍ Scribed by Kiyofumi Yamanishi; Akio Iwashima
- Publisher
- John Wiley and Sons
- Year
- 1985
- Tongue
- English
- Weight
- 601 KB
- Volume
- 123
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Abstract
Intracellular Ca^2+^ sequestration was studied by determining ^45^Ca^2+^ uptake by saponin‐permeabilized Swiss 3T3 mouse fibroblasts. Uptake was enhanced by addition of ATP and was dependent on the concentrations of ATP and saponin. ADP and UTP also enhanced uptake, but less than did ATP. Mitochondrial Ca^2+^ uptake was distinguished from nonmitochondrial uptake by the use of antimycin A plus oligomycin at various Ca^2+^ concentrations. Major sites for sequestration at 10^−5^ M Ca^2+^ are probably mitochondrial and those at 10^−7^ M Ca^2+^ nonmitochondrial, because these drugs inhibited ATP‐dependent Ca^2+^ uptake at 10^−5^ M but not at 10^−7^ M. A23187 completely inhibited uptake, regardless of the Ca^2+^ concentration. Effects of various agents on sequestration were tested; ruthenium red, 2,4‐dinitrophenol, monovalent cation ionophores, and melittin markedly decreased ATP‐dependent Ca^2+^ uptake at 10^−5^ M Ca^2+^. the calmodulin antagonists trifluoperazine (TFP) and W‐7 inhibited Ca^2+^ uptake at both 10^−5^ and 10^−7^ M Ca^2+^, TFP moreso than W‐7, especially at 10^−5^ M. These results suggest that intracellular Ca^+2^ in Swiss 3T3 cells is regulated by mitochondrial and nonmitochondrial Ca^2+^ stores in an ATP‐dependent way and that in a physiological resting state the nonmitochondrial Ca^2+^ store, probably the endoplasmic reticulum, is the major site for the sequestration.