[Hormonal regulation of the heart in aging].

It was established in experiments on adult (8--12 month) and old (26--32 month) rats that in ageing the sensitivity of the cardiovascular system to certain hormones--adrenaline, vasopressin, insulin, thyroxine, estradiol dipropionate--grows while its reactivity to them diminishes. The administration of these hormones causes significant changes in hemodynamics and myocardial contractility. Adrenaline and thyroxine lead to an increase in the blood minute and stroke volume, arterial pressure, cardiac index and left ventricular work index, maximum rate of intraventricular pressure growth, maximum rate of myocardial fiber shortening, and in the contrastility index.

[Interaction between the hypothalamo-hypophyseal system and the thyroid gland during different age periods].

Age peculiarities of interaction of the hypothalamo-hypophysial system and the thyroid gland with consideration to direct and feed-back control were studied. Significant alterations appear in old age in the hypothalamo-hypophysial system and the thyroid gland at the level of direct and feed-back control; there is an increase of sensitivity of the thyroid gland tissue to TSH, and of the hypothalamus-hypophysis--to the T4 effect. This rise of sensitivity is largely determined by the activation of the T4 deiodination processes in the adenohypophysis.

[Thyrotropic activity of the pituitary gland in rats at various age periods].

The thyrotropic activity of the hypophysis (TTH synthesis and secretion) was studied in rats at various age periods. The work was conducted on mongrel male rats of four age groups: 1 1/2-2, 8-10, 18-24, and 28-32-months old. Being relatively low in the sexually immature animals, the thyrotropic activity of the hypophysis considerably intensified in adult rats and diminished with the ageing of the organism.