Light Microscopic Radioautographic Study on RNA Synthesis in the Adrenal Glands of Aging Mice.

Abstract

The aging changes of RNA synthesis and morphology in the adrenal glands of mice from fetal day 19 to 12 months after birth were studied by light microscopic radioautography after 3H-uridine incorporation.Eight groups of mice, each consisting of a litter of 3 individuals, were used. One hour after intraperitoneal injections of 3H-uridine, the adrenal gland tissues were fixed, embedded, sectioned and radioautographed. Quantitative analysis was made on the light microscopic radioautographs.The radioautograms revealed that all types of adrenal gland cells were labeled. In each cell, the grains were localized over the nucleus and the cytoplasm and they were more dense in the nucleus than in the cytoplasm. The activity of RNA synthesis of adrenal glands, as expressed by grain counting, was the highest in the cortex and medulla at fetal day 19, then gradually decreased with aging. In the cortex, the number of silver grains was higher in the zona glomerulosa than those in the other cortical zones from fetal day 19 to 12 months after birth. The number of silver grains was higher in the medulla at embryonic stage than those at the postnatal stages.From these results, it was concluded that the aging changes of RNA synthesis in the adrenal glands of mice were demonstrated.