[The effect of stimulants of the mononuclear phagocytosing system on protein synthesis in rat organs and tissues]

It has been demonstrated in rat experiments that stimulation of the mononuclear phagocytizing system with a polysaccharide intensifies protein biosynthesis in various organs and tissues. In administration of high-polymer RNA into the organism increase of protein synthesis was encountered only in immunocompetent and blood-forming tissues. It is concluded that a stimulating effect in relation to macrophages is characteristic of high-polymer compounds which are absorbed by them due to receptor mediated endocytosis. The differences in the receptor apparatus of the resident macrophages determine the discovered difference in the intensification of protein biosynthesis in the organs and tissues of rats.

[The role of the mononuclear phagocyte system in regulating protein biosynthesis in rat organs and tissues in ontogeny]

In experiments on Wistar rats, we demonstrate that activation of mononuclear phagocytes by a lipopolysaccharide (prodigiosin) results in a marked increase of protein biosynthesis in various organs and tissues. This control mechanism is most distinct in mature rats and undergoes involution in older rats. Cell elements in the mononuclear phagocytes (resident macrophages) originate from the bone marrow. Decrease in the reserve capacity of the bone marrow with age in response to prodigiosin administration suggests an important role of this mechanism during aging.

[The role of the cells of the hepatic sinusoid in regulating protein biosynthesis in hepatocytes]

The protein synthesis in hepatocytes has been shown to be regulated by nonparenchymal (sinusoidal) liver cells. The rate of 14C-leucine incorporation into hepatic proteins and serum proteins was increased during in vivo stimulation of Kupffer cells by lipopolysaccharide (LPS) from Serratia marcescens. Similar results were obtained during a simultaneous cultivation of hepatocytes with nonparenchymal cells, and after the cultivation of hepatocytes in a conditioned medium containing nonparenchymal cells treated with LPS, high density lipoprotein (HDL) and hydrocortisone. The induction of protein synthesis in hepatocytes is presumably associated with the cooperative action of HDL and glucocorticoids.

[The role of nonparenchymal liver cells in activating protein synthesis in hepatocytes upon stimulating the mononuclear phagocyte system with lipopolysaccharide]

It has been found that the rate of hepatocyte protein synthesis depends on the functional state of nonparenchymal liver cells (NPC), of Kupffer cells, in particular. When Kupffer cells were stimulated by intravenously injected lipopolysaccharide (LPS), zymosan or dextran sulfate, the rate of [14C]leucine incorporation into hepatic proteins increased 1.5-2-fold. Similar effects were observed in hepatocytes cocultured with NPC isolated from LPS-stimulated rats as well as in hepatocytes cultured in a conditioned medium from NPC treated with LPS, high density lipoproteins (HDL) and hydrocortisone. It is proposed that apoproteins of HDL resecreted by Kupffer cells may participate in the regulation of hepatocyte gene expression during stimulation of resident macrophages.

[The role of Kupffer cells in regulating protein synthesis in hepatocytes]

Importance of nonparenchymal liver cells for regulation of protein synthesis in hepatocytes was studied using liver cell culture and co-culture. The rate of protein synthesis was increased in hepatocytes during simultaneous cultivation of these cells with nonparenchymal elements. Activation of protein synthesis was distinctly higher in hepatocytes co-cultivated with nonparenchymal liver cells isolated from liver tissue of rats stimulated by bacterial lipopolysaccharide. Similar results were obtained after cultivation of hepatocytes in the conditioned medium containing nonparenchymal liver cells treated with lipopolysaccharide, high density lipoprotein (HDL) and hydrocortisone. The data obtained suggest that nonparenchymal liver cells, especially Kupffer cells, contributed to regulation of protein synthesis in hepatocytes. The cooperative effect of HDL and glucocorticoids in stimulation of the mononuclear phagocytes system appears to be mainly responsible for augmented expression of genes in hepatocytes.

[The role of hepatocytes, Kupffer, and endothelial cells of the liver in blood lipoprotein metabolism]

The rates of blood lipoprotein adsorption by hepatocytes and nonparenchymal cells (NPC) of rat liver have been quantitatively characterized. It was found that the lipoprotein-adsorbing capacity of NPC is higher than that of hepatocytes: 5.6 times for very low density lipoproteins (VLDL), 4.3 times for low density lipoproteins (LDL) and 14.4 times for high density lipoproteins. Stimulation of the mononuclear phagocyte system by a lipopolysaccharide from Serratia marcescens resulted in a significant reduction of blood serum levels of HDL3, LDL and glucocorticoids. Under these conditions the binding of [125I]HDL to hepatocytes increased, while that to Kupffer's cells decreased considerably. In response to stimulation of liver resident macrophages (Kupffer's cells) the rate of protein biosynthesis in hepatocytes increased together with an increase in the rate of [14C]leucine incorporation into the protein component of the blood serum lipoproteins. Enhanced gene expression in the hepatocytes seems to be associated with the cooperative action of HDL and glucocorticoids. Adsorption of lipoproteins by activated Kupffer's cells is due to the receptor-mediated endocytosis, resulting in a decrease of the binding capacity of these cells for HDL and LDL.

[The effect of stimulation of the mononuclear phagocyte system on the binding of high- and low-density lipoproteins by the hepatocytes, Kupffer cells and liver endotheliocytes of rats]

The role of the mononuclear phagocyte system (MPS) in the regulation of low- (LDL) and high-density lipoprotein (HDL) receptor activity in different rat liver cells was investigated. MPS was activated by intravenous administration of bacterial lipopolysaccharide (LPS) from Serratia marcescens. Liver cells were isolated by in vitro perfusion of the liver with a collagenase solution. Separation of Kupffer and endothelial cells was performed by the method of centrifugal elutriation. In control rats, the hepatocytes bound 1.6 times more 125I-HDL and 2.5 times more 125I-LDL per cell than Kupffer cells. Treatment of rats with LPS resulted in a 4.5-fold decrease in the 125I-HDL binding to Kupffer cells. In contrast, the hepatocytes from LPS-treated rat bound 2 times more 125I-HDL than that from untreated rats. The binding of 125I-LDL and 125I-HDL to endothelial cells and 125I-LDL to hepatocytes were not affected by LPS treatment. These results suggest that the MPS (especially Kupffer cells) plays an important role in the regulation of HDL receptor activity in hepatocytes.

[Adrenergic regulation of the level of enkephalins in the myocardium]

Content of enkephalins was increased in myocardium after administration of tyramine (liberator of endogenous catecholamines). Neoepinephrine decreased content of Met-enkephalin in heart. Catecholamines circulating in blood exhibited less distinct effect on content of opioid peptides in myocardium as compared with endogenous free catecholamines. Inverse correlation was found between content of cAMP and Met-enkephalin in myocardium. All the pharmacological drugs studied could exhibit the mediatory effects on opioid peptides in heart via alterations in activity of vegetative nervous system affecting the myocardium.