LIGHT-MICROSCOPIC AUTORADIOGRAPHIC STUDY ON RNA-SYNTHESIS IN THE ADRENAL-GLANDS OF AGING MICE

The aging changes of RNA synthesis and morphology in the adrenal gland s of mice from fetal day 19 to 12 months after birth were studied by l ight microscopic radioautography after H-3-uridine incorporation. Eigh t groups of mice, each consisting of at litter of 3 individuals, were used. One hour after intraperitoneal injections of H-3-uridine, the ad renal gland tissues were fixed, em bedded, sectioned and radioautograp hed. Quantitative analysis was made an the light microscopic radioauto graphs. The radioautograms revealed that all types of adrenal gland ce lls were labeled. In each cell, the grains were localized over the nuc leus and the cytoplasm and they were; more dense in the nucleus than i n the cytoplasm. The activity of RNA synthesis of adrenal glands, as e xpressed by grain counting, was the highest in the cortex and medulla at fetal day 19, then gradually decreased with aging. In the cortex, t he number of silver grains was higher in the zona glomerulosa than tho se in the other cortical zones from fetal day 19 to 12 months after bi rth. The number of silver grains was higher in the medulla at embryoni c stage than those at the postnatal stages. From these results, it was concluded that the aging changes of RNA synthesis in the adrenal glan ds of mice were demonstrated.