Comparative Histological Study of The Structure of Mitochondria, in Cardiac Muscle and Proximal Convoluted Tubules of Adult and Senile Male Albino Rats

Mitochondria are the main source of Adenosine Triphosphate (ATP) in the cell and play a pivotal role in cell life and death. The heart possesses the highest content of mitochondria of any tissue. The greatest density of mitochondria in the kidney is found in the proximal convoluted tubules (PCTs) and the thick ascending limb of loop of Henle. This work aims to compare the histological structure and distribution of mitochondria in cardiac muscle and PCTs of adult and senile male albino rats. Sixteen male albino rats equally classified into four groups: (GI) Adult male cardiac group, (GII) senile male cardiac group, (GIII) Adult male kidney group and (GIV) senile male kidney group. The selected organs were processed for both light microscopic and Transmission electron microscopic (TEM) examinations using H&E, iron hematoxylin stain, uranyl acetate with lead citrate and immuno-histochemical staining technique utilizing Bcl-2 (B cell lymphoma 2) proteins. Morphometric and statistical analysis for the data were done. H&E stained sections showed general histological structure. Iron HX stained sections showed mitochondria as dark multiple small dots or granules. The highest number of mitochondria was detected in (GII) and the lowest number was detected in (GIV). As regards Bcl-2, the highest area percentage was detected in (GII) and the lowest percentage was detected in (GIV). Ultrastructure features for mitochondria based of TEM. The largest size of mitochondria was detected in (GIII). There was reduction in mitochondrial size in aged cardiac muscle and PCTs. The number of mitochondria increased with senility in aged heart but decreased in aged PCTs. Aged mitochondria expressed disorganization of mitochondrial shape and exhibited different types of structural abnormalities.