[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.

[The possible participation of gap junctions in the realization of the effects of stimulators of secretory processes in the hypophysis].

Sodium butyrate and octanol did not change the basal rate of GH secretion. However, octanol completely and partially suppressed GH release stimulated by thyroliberin and DbcAMP, respectively. Octanol did not influence GH secretion induced by DbcGMP.

[Age-related differences in macromolecule biosynthesis reactions in rat pituitary cells to catecholamine, serotonin and acetylcholine].

In experiments using primary monolayer cultures norepinephrine, isoproterenol, and serotonin (10(-6)-10(-5) M) inhibited the rate of total protein biosynthesis more effectively in pituitary cells of pubertal and sexually mature rats as compared to neonates and prepubertal animals. Acetylcholine (10(-5)M) reduced the rate of total protein synthesis in pituitary cells of pubertal rats but did not change this parameter of functional activity in pituitary cells of neonatal animals. Norepinephrine and isoproterenol inhibited the rate of DNA synthesis in pituitary cells of newborn rats whereas serotonin and acetylcholine were of no avail in this respect.

[Increased sensitivity of hypophyseal cells from neonatal rats to bromocriptine and melatonin].

Age-related peculiarities of the bromocriptine and melatonin effect on macromolecule biosyntheses in cultured rat pituitary cells were studied during long-term (3 day) incubation. Bromocriptine (10(-9)-10(-7) M) caused dose-dependent inhibition of DNA synthesis in pituitary cells of neonatal rats, but only in maximal dose (10(-7) M) it decreased significantly this parameter in pituitary cells of adult animals. Melatonin (10(-8)-10(-6) M) caused significant inhibition of DNA synthesis in cultured cells of neonatal rat pituitaries.

[The cytoarchitectonics of the adenohypophysis in light of the concepts of cellular flows].

Analysis of published data allows to suggest a possible model of adenohypophyseal cytoarchitectonics based on the concepts of tissue self-renewal and streaming in this gland. The model provides a framework for understanding: a) the existence of ambiguous cellular elements; b) change of relationship between different types of hormone secreting cells with sex-dependent prevalence of somato- or lactotrophs; c) relatively high proliferative activity of lactotrophs in mature pituitary gland; d) specific spatial arrangement of various types of hormone secreting cells; e) multiple effects of some bioregulators on the secretion of two or more pituitary hormones; f) the existence of polyfunctional pituitary adenomata containing and secreting several adenohypophyseal hormones simultaneously. Possible approaches to thorough evaluation and testing of the model in experiments using organ or cell cultures of adenohypophysis are discussed.

[Secretory activity of lactotrophs and its regulation by hypothalamic hormones in primary cultures of pituitary cells of rats of different ages].

Basal prolactin (PRL) secretion and the responses of lactotrophs to thyroliberin, dopamine and somatostatin were studied in the experiments employing primary monolayer cultures of pituitary cells obtained from developing rats of different ages. High responsiveness of PRL-secreting cells to the action of hypothalamic hormones was observed in the group of neonatal rats, although basal PRL release was about two orders lower in pituitary cultures of neonatal rats as compared to the cultures of immature, pubertal and adult animals. The investigation performed could reveal quantitative, but not qualitative differences in the reactions of lactotrophs of various age groups.

[Enhanced sensitivity of pituitary cells to corticosteroids in neonatal rats].

The effects of corticosteroids on pituitary cells, obtained from developing rats of different ages, were studied during long-term (3-4 days) incubation. Dexamethasone, cortisol and aldosterone inhibited the rate of DNA synthesis in primary cultures of pituitary cells from neonatal and pup rats more efficiently than in cell cultures of prepubertal and adult animals. Moreover, the above mentioned corticosteroids inhibited total protein biosynthesis in pituitary cells of infantile rats and did not change significantly this index of functional activity in cells of prepubertal and adult animals.

[Reactions of rat fetal hepatocytes to hormones in primary cultures grown in selective media with an addition of glucocorticoid and barbiturate].

After growing of fetal rat hepatocytes in the medium containing cortisol and sodium barbital for 4-8 days and subsequent cultivation in the medium without glucocorticoid and barbiturate for 1-4 days insulin retained its ability to stimulate total RNA and protein synthesis, while human growth hormone kept its enhancing action on RNA biosynthesis. However, cortisol did not change protein synthesis and inhibited paradoxically incorporation of 3H-uridine into total RNA, after preincubation of cells in the selective medium. This suggests that prolonged exposure of cultured fetal rat liver cells to cortisol and sodium barbital may cause phenomena similar to those of hormonal and/or enzymatic imprinting.

[Effects of dibutyryl derivatives of cyclic nucleotides on synthesis of total RNA and proteins in cultured fetal rat hepatocytes].

During short-term (6 h) or long-term (24 h) incubation of fetal rat liver cells in primary cultures, 10(-3) M dibutyryl-derivative of cyclic AMP (Bt2cAMP) and sodium butyrate decreased total RNA and protein synthesis. In contrast, dibutyryl-cyclic GMP (Bt2cGMP) at the same dose (10(-3) M) was without significant effect on RNA and protein biosynthesis. During short-term (4 h) incubation 10(-3) M Bt2cAMP and Bt2cGMP stimulated serum albumin production, while sodium butyrate was without effect.

[The direct stimulating action of thyroliberin on the biosynthesis of total protein in cultured liver cells of rat fetuses].

In experiments using fetal rat liver cultured cells TRH was shown to stimulate total protein synthesis but not RNA synthesis during long incubation. Somatostatin affected neither protein synthesis nor RNA synthesis in cultured liver cells. Possible physiological role of peripheral TRH during perinatal period in the rat is discussed.

[An analysis of the distribution by molecular weight of an aggregate of biologically active compounds taking into account their possible penetration through gap-junction channels].

Analysis of molecular weight distribution of most well-known biologically active compounds demonstrates that all known types of bioregulatory compounds, excluding most peptides, have molecular mass less than 800 Da, i.e. they may penetrate the gap junction channels and, hence, play a part of intratissue regulators.

[The effect of dibutyryl derivatives of cyclic nucleotides on albumin production in a primary culture of rat liver cells].

Dibutyryl-derivative of cyclic AMP (Bt2cAMP, 10(-3)M) affected the basal and cortisol-induced production of immunoreactive serum albumin (SA) in primary cultures of fetal rat liver cells by the type of two-phase time dependency. The same two-phase character exhibited dose-dependent effect of Bt2cAMP (10(-5)-10(-3)M) on SA production in cultured liver cells obtained from fetal and 3 weeks old rats. Similar two-phase dose- and time-dependent effects demonstrated Bt2cGMP (10(-5)-10(-3)M), although certain differences were detected when either action of Bt2cAMP and Bt2cGMP or response of cultured liver cells from fetal and early postnatal rats to these drugs were studied.

[Hormonal regulation of total RNA and protein biosynthesis in liver cell cultures of rats in the pre- and postnatal period of development].

The effects of several hormones on total RNA and protein biosynthesis were examined in primary cultures of liver cells obtained from rat fetuses on 21-22 days of gestation and from 3 week-old weanling rats. The intensity of biosynthesis processes was estimated by the incorporation of labeled precursors in macromolecules. Insulin, cortisol, triiodothyronine (T3) stimulated RNA and protein biosynthesis in both types of cultures.

[Effect of synthetic analogs of the sex steroid hormones on the secretory and proliferative activity of the adenohypophysis in vivo and in vitro in rats].

Synthetic steroid compounds STS 557 and STS 737 administered to ovariectomized rats increased prolactin secretion to a lesser extent than estradiol benzoate or estrogen J 271. When injected to estradiol benzoate treated ovariectomized rats, compounds STS 557, STS 737 and progesterone failed to change DNA synthesis in the adenohypophysis and prolactin secretion. Only compound STS 737 exerted a pronounced effect on the adenohypophyseal cells in primary cultures.

[Effect of a conditioned medium of pinealocytes on prolactin secretion in primary culture of adenohypophyseal cells of male rats].

Conditioned medium of pinealocytes (CMP, 18-20%) added to primary cultures of rat pituitary cells for 1.5 h changed neither the basal rate of PRL secretion nor dopamine-inhibited release. However CMP markedly attenuated PRL secretion induced by thyroliberin or isobutyl-menthylxanthine.

[Biological properties of structural analogs of thyroliberin].

Effects of 8 synthetic tripeptides--structural analogues of thyroliberin (TRH)--in basal and TRH-induced secretion of prolactin (PRL) and thyrotropin (TSH) were studied in primary cultures of rat pituitary cells. 7 tripeptides had chemical structure Pyr-Ser-X-NH2, where X was Leu, Val, Asn, Ala, Ile, Met, Phe. One tripeptide had the structure Pyr-Ser-Gly-OCH3.

DNA synthesis in lactotrophs of primary rat anterior pituitary cell cultures. Effects of thyroliberin, bromocriptine and somatostatin.

Prolactin immunostaining in combination with thymidine autoradiography was used to characterize changes in the DNA-synthesizing activity of lactotrophs in primary monolayer cultures of the rat anterior pituitary gland treated for 3 days with thyroliberin (TRH), somatostatin (SRIF) and bromocriptine (CB 154). The number of lactotrophs labelled with 3H-thymidine within the total pool of labeled pituitary cells was used to estimate DNA synthesis in prolactin-producing cells. TRH (10 ng/ml) stimulated DNA synthesis in the whole population of cultured cells but not in lactotrophs.