Reduced calcium uptake by mitochondria in pyruvate dehydrogenase -deficient human diploid fibroblasts. Padua, Rodolfo A., Kyle T. Baron, Bhaskar Thyagarajan, Colin Campbell, and Stanley A. Thayer. Department of Pharmacology, University of Minnesota Medical School, Minneapolis, MN 55455
APStracts 4:0322C, 1997.
Physiological and pathological Ca2+ loads are thought to be taken up by mitochondria via a process dependent on aerobic metabolism. We sought to determine whether human diploid fibroblasts from a patient with an inherited defect in pyruvate dehydrogenase exhibit a decreased ability to sequester cytosolic Ca2+ into mitochondria. Mobilization of Ca2+ stores with bradykinin increased the cytosolic Ca2+ concentration ([Ca2+]c) to comparable levels in control and pyruvate dehydrogenase-deficient fibroblasts. In normal fibroblasts transfected with plasmid DNA encoding mitochondrial-targeted apoaequorin, bradykinin elicited an increase in Ca2+-dependent aequorin luminescence corresponding to an increase in the mitochondrial Ca2+ concentration ([Ca2+]mt) of 2.0 0.2 M. The mitochondrial uncoupling agent, FCCP, blocked the bradykinin-induced [Ca2+]mt increase although it did not affect the [Ca2+]c transient. Basal [Ca2+]c and [Ca2+]mt in control and pyruvate dehydrogenase -deficient cells were similar. However, confocal imaging of the potential-sensitive dye JC-1, indicated that the number of highly polarized mitochondria was reduced from 30 1 % in normal cells to 19 2 % in the pyruvate dehydrogenase-deficient fibroblasts. Bradykinin -elicited [Ca2+]mt transients in pyruvate dehydrogenase-deficient cells were reduced to 4 % of control, indicating that pyruvate dehydrogenase-deficient mitochondria have a decreased ability to take up cytosolic Ca2+. Thus, cells with compromised aerobic metabolism have a reduced capacity to sequester Ca2+. 

Received 5 June 1997; accepted in final form 17 October 1997.
APS Manuscript Number C299-7.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 14 November 1997