Effect of Nitric Oxide on the Functioning of the P-Glycoprotein Transporter.

We studied the effect of nitric oxide (NO) on the functioning of P-glycoprotein transporter (Pgp) in Caco-2 cells. NO donor S-nitrosoglutathione (GSNO) was used in concentrations of 1, 10, 50, 100, and 500 µM; the duration of exposure was 24 h. The content of Pgp was analyzed by the Western blotting, activity of the transport protein was analyzed by the transport of its substrate fexofenadine. It was shown that GSNO in concentrations of 10 and 50 µM increased the content and activity of Pgp. Increasing the GSNO concentration to 500 µM led to the development of nitrosative stress and a decrease in the content and activity of the transporter protein.

[Functioning of pregnan X receptor under conditions of nitrosative stress]. / Funktsionirovanie pregnan X retseptora v usloviiakh nitrozativnogo stressa.

Pregnan X receptor (PXR) is a nuclear receptor that plays an important role in the regulation of the expression of biotransformation and metabolic enzymes. The functioning and possible mechanisms of PXR regulation under conditions of nitrosative stress have not been studied, which served as the purpose of this study. The work was performed on Caco-2 cells. Nitrosative stress (NS) was modeled using S-nitrosoglutathione (GSNO) at concentrations of 1 µM, 10 µM, 50 µM, 100 µM, and 500 µM and incubation during of 3 h, 24 h, and 72 h. The amount of PXR was assessed byWestern blotting. Incubation of Caco-2 cells with all concentrations GSNO for 3 h led to a decrease in the amount of PXR. Incubation with GSNO (1-50 µM) for 24 h was accompanied by an increase in the amount of PXR, while at a concentration of 100 µM this indicator did not significantly differ from the control, at a concentration of 500 µM it was lower. Prolonged incubation (72 h) enhanced NS and led to a normalization (1 µM GSNO) or a decrease of the PXR level (10-500 µM GSNO). The induction of PXR by GSNO was mediated by the effect of the nitrosative stress product bityrosine on the transcription factor. It was shown that bityrosine at concentrations of 0,4 mM and 1 mM increased the amount of PXR.

Effects of crops on the humus accumulation process in the grey forest soils of Priangarye.

The influence of a number of agricultural plants in the crop rotation on the grey forest soils in the Irkutsk Region upon the intensity of the humification process was investigated by means of microbiological and biochemical tests. The synthesis, decomposition, and the accumulation ratio of humus were concluded from the phenoloxidase activity. The cellulose-decomposing microflora and algaeflora were taken into consideration as well. The humus synthesis processes were most active in the wheat and lucerne plots, they were less effective in the fallow and virgin soils. The lack of organic matter in the permanent fallow soil cuts down the humus accumulation ratio and the counts of microorganisms. The soil cultivation intensifies the humus synthesis processes and changes the composition of microorganisms in the soil. Algae which are mainly represented by green and blue-green species are an additional source of organic substance in the soil. Decomposition of organic substances in the soil proceeds with an active participation of cellulose decomposers which are mainly represented by fungal and bacterial flora. In rare cases actinomycetes can be found. Application of mineral fertilizers intensifies the humus accumulation process and improves the qualitative and quantitative composition of microflora in all the plots under investigation.