[Role of calcium ions and cyclic nucleotides in the regulation of somatotroph functional activity in rats as a function of age].

Somatotropic hormone (STH) biosynthesis and secretion were studied in primary adenohypophyseal cultures of neonatal, prepubertal, and adult rats. It was shown by disc PAAG electrophoresis of products synthesized in incubation of neonatal rat hypophyseal cells that L-14C leucin incorporates predominantly in the STH containing fraction. The share of prelabeled STH secreted into the culture virtually did not depend on the age of animals, this indicating the maturity of mechanisms of basal somatotroph secretion as early as in the neonatal period of development.

[The effect of insulin on protein synthesis and secretion in primary liver cultures].

The effects of insulin on the rates of synthesis of intracellular and secreted proteins have been studied in primary cultures of fetal rat hepatocytes. During 3-h incubation with the hormone and 14C-L-leucine similar stimulation of synthesis of both intracellular and secreted protein was observed. Insulin did not affect significantly the proportion of 14C-labelled proteins destined for secretion in the cell cultures grown on standard nutrient medium, as well as on selective medium containing phenobarbital and cortisol.

[Effect of steroid hormones and noradrenaline on somatotropin hormone secretion by primary cultures of hypophyseal cells of rats of various ages].

Dexamethasone and aldosterone in concentrations 10(-8) to 10(-6) stimulated STH secretion by hypophyseal cells of neonatal and adult rats under conditions of prolonged (72 h) incubation of primary cultures. Corticosterone and progesterone had a stimulating effect on STH release by hypophyseal cells. Long exposure of cultured suckling rat cells to dexamethasone resulted in increase of STH basal secretion and enhanced the stimulating effect of low concentration (10(-7) mole) of noradrenaline on STH release during a subsequent short (2 h) incubation.