Morphologic, biochemical and molecular mitochondrial changes during reperfusion phase following brief renal ischemia.
Ischemia/reperfusion of organs and cells induces apoptosis through a complicated series of changes in mitochondria, mainly the generation of oxygen free radicals, permeability transitions, calcium translocations, and release of apoptogenic factors such as cytochrome c and Bcl-2 family members. The liberation of these factors occurs very early after reoxygenation and it has been assumed that it takes place without any structural alteration of the mitochondrial membranes. The aim of this study was to detect ultrastructural changes of mitochondria in the initial stages of reperfusion at the time when Bcl-2 and succinic dehydrogenase, located in the outer and inner membranes, respectively, were released. Ischemia/reperfusion was produced in adult rats by clamping one renal artery for 60 min and reoxygenating for 60, 120, 180, and 240 min. A model of chemical hypoxia with intra-arterial 50 mM sodium azide served as comparison, allowing free blood flow for 30, 60, 120 and 180 min. Light and electron microscopy, immunostaining for Bcl-2, and enzyme histochemistry for succinic dehydrogenase were performed. Our results showed mitochondrial swelling, rupture of inner and outer membranes, and leakage of mitochondrial matrix into the cytoplasm in ischemia after 120 min of reperfusion. Bcl-2 immunoreactivity and focal lowering of SDH reactivity were also noted and became more pronounced at the same time that the mitochondrial ultrastructure demonstrated more evident changes including rupture of the inner and outer membranes. Our studies seem to indicate that in early ischemia-reperfusion and in chemical hypoxia-induced apoptosis, the earliest ultrastructural changes take place in mitochondria and that swelling and rupture of mitochondrial membranes occur in parallel with the loss of Bcl-2 and SDH activity.
Benítez-Bribiesca
L
L
Unidad de Investigación Médica en Enfermedades Oncológicas, Hospital de Oncología, Centro Médico Nacional S-XXI, Instituto Mexicano del Seguro Social, México, D.F., México. luisbenbri@mexis.com
Gómez-Camarillo
M
M
Castellanos-Juárez
E
E
Mravko
E
E
Sánchez-Suárez
P
P
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015687:Cell Hypoxia; D007425:Intracellular Membranes / Q000648:ultrastructure; D007668:Kidney / Q000098:blood supply / Q000502:physiology / Q000648:ultrastructure*; D008297:Male; D008854:Microscopy, Electron; D008928:Mitochondria / Q000502:physiology* / Q000648:ultrastructure*; D008933:Mitochondrial Swelling; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000473:pathology* / Q000503:physiopathology; D013385:Succinate Dehydrogenase / Q000378:metabolism
D019253:Proto-Oncogene Proteins c-bcl-2; D013385:Succinate Dehydrogenase