Electron microscopic radioautographic study on mitochondrial RNA synthesis in adrenal cortical and medullary cells of aging mice

Tetsuji Nagata

doi:10.4236/jbise.2011.43031

Abstract

In order to study the aging changes of intramito-chondrial RNA synthesis of mouse adrenal cells, 10 groups of developing and aging mice, each consisting of 3 individuals, total 30, from fetal day 19 to postna-tal newborn at day 1, 3, 9, 14, adult at month 1, 2, 6 and senescent animals at month 12 (year 1) and 24 (year 2) were injected with 3H-uridine, an RNA pre-cursor, sacrificed 1 hr later and the adrenal tissues were fixed and processed for electron microscopic radioautography. On electron microscopic radio-autograms obtained from each animal, the number of mitochondria per cell, the number of labeled mito-chondria with 3H-uridine showing RNA synthesis per cell and the mitochondrial labeling index in each adreno-cortical cells, in 3 zones, as well as in each adreno-medullary cells, 2 types of cells in the medulla, the adrenalin cells and the noradrenalin cells, were calculated and the results in respective aging groups were compared with each others. The results demon-strated that the number of mitochondria in adreno-cortical cells in 3 zones, the zona glomerulosa, fasciculata and reticularis of respective mice at vari-ous ages increased from fetal day 19 to postnatal month 1 reaching the plateau from month 1 to 24 due to development and aging of animals, respectively, while the number of labeled mitochondria per cell and the labeling index of intramitochondrial RNA synthesis incorporating 3H-uridine increased from fetal day 19 to postnatal month 2, reaching the maxima and decreased slightly from month 6 to month 24. On the other hand, the number of mito-chondria per cell in the medulla increased from fetal day 19 to postnatal month 1 reaching the plateau from month 1 to 24, while the number of labeled mi-tochondria per cell and the labeling index of in-tramitochondrial RNA synthesis increased from fetal day 19 to postnatal day 14, reaching the maxima and decreased from month 1 to 24. From the results, it was demonstrated that the activity of intramitochno-drial RNA synthesis in both the cortical and me-dullary cells in developing and aging mice adrenals changed due to aging of individual animals.

Highlights

Intramitochondrial nucleic acid syntheses, both DNA and RNA, in mammalian and avian cells were first demonstrated morphologically by the present author by means of electron microscopic radioautography in primary cultured cells of the livers and kidneys of mice and chickens in vitro [1,2] and in some other established cell lines such as HeLa cells [3,4,5,6] or mitochondrial fractions prepared from in vivo cells [7,8,9]
The results demonstrated that the number of mitochondria in adrenocortical cells in 3 zones, the zona glomerulosa, fasciculata and reticularis of respective mice at various ages increased from fetal day 19 to postnatal month 1 reaching the plateau from month 1 to 24 due to development and aging of animals, respectively, while the number of labeled mitochondria per cell and the labeling index of intramitochondrial RNA synthesis incorporating 3H-uridine increased from fetal day 19 to postnatal month 2, reaching the maxima and decreased slightly from month 6 to month 24
The number of mitochondria per cell in the medulla increased from fetal day 19 to postnatal month 1 reaching the plateau from month 1 to 24, while the number of labeled mitochondria per cell and the labeling index of intramitochondrial RNA

Summary

Introduction

Intramitochondrial nucleic acid syntheses, both DNA and RNA, in mammalian and avian cells were first demonstrated morphologically by the present author by means of electron microscopic radioautography in primary cultured cells of the livers and kidneys of mice and chickens in vitro [1,2] and in some other established cell lines such as HeLa cells [3,4,5,6] or mitochondrial fractions prepared from in vivo cells [7,8,9]. This paper deals with the relationship between the RNA synthesis and the aging in the adreno-medullary cells of mice in vivo at various developmental stages from fetal day 19 to postnatal month 2 and further to adult and senescent stages up to month 24 (year 2) during aging by means of electron microscopic radioautography as a part of serial studies on special cytochemistry [49] and radioautographology [50]

Methods

Results

Discussion

Conclusion