Expression of Cyt-c-Mediated Mitochondrial Apoptosis-Related Proteins in Rat Renal Proximal Tubules during Development.
BACKGROUND
Apoptosis regulates embryogenesis, organ metamorphosis and tissue homeostasis. Mitochondrial signaling is an apoptotic pathway, in which Cyt-c and Apaf-1 are transformed into an apoptosome, which activates procaspase-9 and triggers apoptosis. This study evaluated Cyt-c, Apaf-1 and caspase-9 expression during renal development.


METHODS
Kidneys from embryonic (E) 16-, 18-, and 20-day-old fetuses and postnatal (P) 1-, 3-, 5-, 7-, 14-, and 21-day-old pups were obtained. Immunohistochemical analysis, dual-labeled immunofluorescence, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) technique assay and Western blot were performed in addition to histological analysis.


RESULTS
Immunohistochemistry showed that Cyt-c was strongly expressed in proximal and distal tubules (DTs) at all time points. Caspase-9 and Apaf-1 were strongly expressed in proximal tubules (PTs) but only weakly expressed in DTs. Dual-labeled immunofluorescence showed that most tubules expressed both Cyt-c and Apaf-1, except for some tubules that only expressed Cyt-c. The TUNEL assay showed a greater percentage of apoptotic cells in PTs compared to DTs. Apaf-1 and cleaved caspase-9 protein expression gradually increased during the embryonic period and peaked during the early postnatal period but apparently declined from P7. Cyt-c protein expression was weak during the embryonic period but obviously increased after P1.


CONCLUSIONS
This study showed that PTs are more sensitive to apoptosis than DTs during rat renal development, even though both tubule segments contain a large number of mitochondria. Furthermore, Cyt-c-mediated mitochondrial apoptosis-related proteins play an important role in PTs during the early postnatal kidney development.
Department of Histology and Embryology, Jinzhou Medical University, Jinzhou, China.
Xiao-Feng
XF
Song
He
H
Tian
Ping
P
Zhang
Zhen-Xing
ZX
Zhang
D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D053477:Apoptotic Protease-Activating Factor 1 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism*; D005260:Female; D007150:Immunohistochemistry; D007687:Kidney Tubules, Proximal / Q000196:embryology / Q000254:growth & development* / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley
C506594:Apaf1 protein, rat; D051017:Apoptosis Regulatory Proteins; D053477:Apoptotic Protease-Activating Factor 1; D024101:Mitochondrial Proteins; D045304:Cytochromes c; C506435:Casp9 protein, rat; D053453:Caspase 9