On the role of mitochondria in cell injury caused by vanadate-induced Ca2+ overload.
Incubation of isolated rat hepatocytes with vanadate (0.25, 0.5 and 1 mM) resulted in progressive accumulation of Ca2+ in the intracellular compartments. Vanadate- induced Ca2+ accumulation was related to inhibition of the plasma membrane Ca2+-extruding system, but did not involve either enhanced plasma membrane permeability to Ca2+ or the enhanced operation of a putative Na+/Ca2+ exchanger. After an initial rise in the cytosolic free Ca2+ concentration, as revealed by phosphorylase activation, Ca2+ was sequestered predominantly by the mitochondria with little contribution from the endoplasmic reticulum. As the amount of Ca2+ in the mitochondria increased, a progressive decrease in mitochondrial membrane potential occurred, together with an impairment of the ability of these organelles to further sequester Ca2+. Associated with this, there was a decrease in intracellular ATP level, formation of surface blebs and cytotoxicity. Addition of an uncoupler to vanadate-treated hepatocytes dramatically accelerated the appearance of plasma membrane blebs and toxicity. Our results demonstrate that under conditions in which the plasma membrane Ca2+ pump is inhibited, mitochondria play an important role in protecting hepatocytes against damage induced by Ca2+ overload.
Richelmi
P
P
Istituto di Farmacologia II, University of Pavia, Italy.
Mirabelli
F
F
Salis
A
A
Finardi
G
G
Berte
F
F
Bellomo
G
G
D000255:Adenosine Triphosphate / Q000032:analysis; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D005978:Glutathione / Q000032:analysis; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008930:Mitochondria, Liver / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D014638:Vanadates / Q000633:toxicity*
D014638:Vanadates; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000255:Adenosine Triphosphate; D005978:Glutathione; D002118:Calcium