[Neurohumoral control of protein biosynthesis during aging]

It has been shown in the experiments on adult (6-8 mo) and old (26-28 mo) Wistar rats that in aging, due to an electrical stimulation of the hypothalamus, the liver induction of thyroxine aminotransferase, tryptophan-pyrrolase, glucose-6-phosphatase and fructose-1, 6-diphosphatase decreases. In old rats, the biosynthesis of RNA fractions gets activated at later periods. In contrast to adult animals, the electrical hypothalamic stimulation did not induce any marked changes in chromatin fractions ratio and transcriptional processes in old rats. With aging, it may happen that the target cells cannot respond to adequate stimulations, while the central (hypothalamic, in particular) mechanisms cannot realize them. In aging, the influence of the hormones (insulin, testosterone, thyroxin and hydrocortisone) on the synthesis of proteins-invertors, regulating plasmatic membrane state Is weakened. Following surgical denervation of the liver in old rats, the less marked changes in RNA and protein synthesis and lesser influences on monooxygenase induction were found in old rats. All these observations indicate an impairment of the neural control over protein biosynthesis in senescence. Also, the axonal transport of proteins is delayed in old rats that may influence the nervous cell aging. Owing to all these shifts, the plastic provision of body integrative reactions is impaired.