Calcium transport and inner mitochondrial membrane damage in renal cortical mitochondria.
Ca2+ uptake and efflux processes, as they are manifested during procedures used for isolation of renal cortical mitochondria, were characterized in order to provide a better basis for making inferences from isolated mitochondria about the in vivo state of mitochondrial Ca2+ homeostasis in both normal and injured tissues and to better define the mechanisms by which Ca2+ mediates injury to renal cortical mitochondria. Mitochondrial Ca2+ uptake predictably occurred when the capacity of the Ca2+ chelator added to the isolating medium to maintain free Ca2+ in the submicromolar range was exhausted unless ruthenium red was present to specifically inhibit the Ca2+ uniport. Ca2+ uptake during isolation ultimately led to loss of accumulated Ca2+ and intramitochondrial K+ as well as to deterioration of respiratory function. Extramitochondrial Ca2+ also evoked the latter two events in the absence of Ca2+ uptake but only at much higher medium Ca2+ levels than were required when Ca2+ uptake was allowed to occur. Studies using mitochondria loaded with known amounts of Ca2+ at 4 degrees C and then subjected to a reisolation procedure including all the steps of normal isolation demonstrated that phosphate markedly potentiated Ca2+-induced alterations of mitochondrial membrane permeability properties. Of several agents studied singly, fatty acid-free albumin was most effective in blocking Ca2+ + phosphate-induced alterations of mitochondrial membrane permeability. The protective effect of fatty acid-free albumin was further enhanced by combining it with Mg2+, dibucaine, or oligomycin + ADP. This study thus quantitatively defined conditions under which Ca2+ uptake can be expected to occur during mitochondrial isolation, demonstrated that the effects of this Ca2+ uptake on mitochondrial properties are similar to those previously elucidated in mitochondria studied at warmer temperatures, and defined methods suitable for blocking such Ca2+ movements and their deleterious effects.
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002458:Cell Fractionation; D003992:Dibucaine / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D007672:Kidney Cortex / Q000648:ultrastructure*; D008274:Magnesium / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D009840:Oligomycins / Q000494:pharmacology; D010101:Oxygen Consumption; D010710:Phosphates / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D009840:Oligomycins; D010710:Phosphates; D000244:Adenosine Diphosphate; D008274:Magnesium; D003992:Dibucaine; D011188:Potassium; D002118:Calcium