Electron Microscopic Radioautographic Study on Protein Synthesis in Hepatocyte Mitochondria of Aging Mice

Abstract

For the purpose of studying the aging changes of intramitochondrial protein synthesis in mouse hepatocytes, 10 groups of aging mice, each consisting of 3 individuals (total 30), from fetal day 19 to postnatal month 24, were injected during development with 3H-leucine, a protein precursor, sacrificed 1 h later, and the liver tissues processed for electron microscopic (EM) radioautography. On EM radioautograms obtained from each animal, the number of mitochondria, the number of labeled mitochondria, and the mitochondrial labeling index labeled with silver grains due to H-leucine showing protein synthesis in each mononucleate hepatocytes were counted and the averages in respective aging groups were compared. From the results, it was demonstrated that the numbers of mitochondria, the numbers of labeled mitochondria, and the labeling indices of intramitochondrial protein syntheses in mononucleate hepatocytes of mice at various ages from embryonic day 19 to postnatal month 24 increased and decreased due to development and aging of animals.

A method for measuring mitochondrial mass and activity

“…The number, structure and functions of mitochondria differ in animal cells and tissues in relation to the energetic needs (Yaffe 1999;Nagata 2006). As the energy demands of cells can vary during development and differentiation, and in response to physiological or environmental alterations (Pollak and Sutton 1980;Cuezva et al 1997;Enriquez et al 1999), the number of mitochondria can change by complex and finely regulated processes (Goffart and Wiesner 2003;Hood 2001;Klingenspor et al 1996).…”

Effects of cadmium chloride on some mitochondria-related activity and gene expression of human MDA-MB231 breast tumor cells

“…In addition, these organelles are involved in the synthesis of amino acids, nucleotides, and lipids, in ion homeostasis and in cell proliferation, motility and programmed death [27][28][29]. The number, structure, and functions of mitochondria differ in animal cells and tissues in relation to the energetic needs [30,31], and in response to physiological or environmental alterations [32][33][34]. Malfunctioning mitochondria are related to aging and to many diseases, including cancer [35][36][37].…”

<b>Aging Changes of Macromolecular Synthesis in the Mitochondria of Mouse Hepatocytes as Revealed by Microscopic Radioautography</b>

“…2A), 9 and 14 (Fig. 2B), to adult and senescent stages at postnatal month 1-24 (Nagata & Ma, 2005a,b;Nagata, 2007a). The silver grains were also observed in binucleate hepatocytes at postnatal day 1 to month 24.…”

“…3C), 6 , 12 and 24. Silver grains observed over the mitochondria were located mainly on the mitochondrial matrices, but a few over their nuclei, cytoplasmic matrix, endoplasmic reticulum, ribosomes, Golgi apparatus and mitochondria (Nagata, 2006a(Nagata, ,b, 2007c. In the mitochondria, the silver grains were over the mitochondrial membranes and cristae when observed by high power magnification (Fig.…”