Morphology of mitochondrial permeability transition: morphometric volumetry in apoptotic cells.
Here we report on the mitochondrial permeability transition (MPT), which refers to the morphology of mitochondria whose inner membrane has lost its selective permeability. In all types of apoptotic cells so far examined, we found outer mitochondrial membranes that had been ruptured. These mitochondria present a swollen matrix covered by an inner membrane herniating into the cytoplasm through the breached outer membrane. Similarly ruptured outer mitochondrial membranes have been reported in studies on mitochondrial fractions induced to undergo MPT, carried out by others. Our observations were made on five types of rat tissue cells and six different cultured cell lines in the early stages of apoptosis. Samples from the cell lines HL-60, HeLa, WEHI-164, and a special batch of PC-12 cells were subjected to various apoptogenic agents and analyzed morphometrically. Nonapoptotic companion cells with unaltered nuclear structure (CUNS) were also analyzed. The mitochondrial volume in microm(3) and the volume fraction of the cytoplasm occupied by mitochondria in cells with typical nuclear signs of apoptosis and also in CUNS were evaluated. The volume of the mitochondria with ruptured membrane represents at least 69% (47-89%) of the total mitochondrial volume of the apoptotic cells. Thus, a considerable fraction of the cellular mitochondrial mass is or was in the state of permeability transition and probably involved in enhancement of the apoptotic program. In all samples, a fraction of the cells with normal nuclei possessed mitochondria with breached outer membranes as described above. In these cells, MPT occurred before the appearance of the typical nuclear phenotype of the apoptotic cells.
Sesso
Antonio
A
Laboratory of Immunopathology, Institute of Tropical Medicine, University of São Paulo, Av. Enéas de Carvalho Aguiar, 500 Prédio II 2o andar, CEP 05403-000 São Paulo, SP, Brazil. antses88@uol.com.br
Marques
Márcia M
MM
Monteiro
Maria M T
MM
Schumacher
Robert I
RI
Colquhoun
Alison
A
Belizário
José
J
Konno
Sérgio N
SN
Felix
Tahis B
TB
Botelho
Luis A A
LA
Santos
Vanessa Z C
VZ
Da Silva
Guilherme R
GR
Higuchi
Maria de L
Mde L
Kawakami
Joyce T
JT
D000818:Animals; D017209:Apoptosis; D005260:Female; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism / Q000648:ultrastructure; D008297:Male; D008321:Mammary Glands, Animal / Q000378:metabolism / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000737:chemistry* / Q000378:metabolism*; D010539:Permeability; D010950:Plasma Cells / Q000378:metabolism / Q000648:ultrastructure; D011467:Prostate / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D014407:Tumor Cells, Cultured / Q000648:ultrastructure