Mitochondrial Ca2+ uptake at submicromolar [Ca2+]i in permeabilised pancreatic acinar cells.
We studied the uptake of Ca2+ in different intracellular Ca2+ pools by use of steady-state measurement of 45Ca2+ in a preparation of digitonin-permeabilized pancreatic acinar cells. The Ca2+ content of all intracellular pools was assessed at different free Ca2+ concentrations between 0.1 and 1 microM. At low Ca2+ concentrations, almost 50% of Ca2+ was taken up, ATP-dependent, in a non-mitochondrial pool. Even at 0.1 microM free Ca2+ the mitochondrial Ca2+ pool contained 26% (3.4 +/- 0.8 nmol Ca2+/mg prot) of the total Ca2+ and this percentage was increased to 49% at 1 microM Ca2+ (16.7 +/- 1.1 nmol Ca2+/mg prot). Our data also show that the uptake into the non-mitochondrial pool can be further differentiated on the basis of ATP-dependence, and that the ATP-independent uptake has a biphasic dependency on the free Ca2+ concentration.
Toescu
E C
EC
Physiological Laboratory, MRC, Liverpool, UK.
Gardner
J M
JM
Petersen
O H
OH
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004072:Digitonin; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D010179:Pancreas / Q000166:cytology / Q000378:metabolism*; D010539:Permeability
D000255:Adenosine Triphosphate; D004072:Digitonin; D002118:Calcium