Swelling-induced K+ influx in cultured primary astrocytes.

The effect of swelling of cultured primary astrocytes from rat brain in hypotonic medium on K+ influx has been studied. A decrease in osmolality from 310 to 180 mOsm increased the activity of sodium pump (ouabain-inhibited 86Rb+ influx) and Na+,K+,2Cl- cotransport (ouabain-insensitive bumetanide-inhibited 86Rb+ influx) by 70 and 35%, respectively. It is suggested that activation of these transport systems makes it possible to retain a high potassium concentration in the cells under regulatory volume decrease.

[The effect of opioid peptides on a decreased proliferation and on an increased maturation rate of glioma C-6 cells manifested by enhanced marker enzyme activity]. / Vliianie opioidnykh peptidov na snizhenie proliferatsii i uvelichenie skorosti sozrevaniia kletok gliomy C-6, proiavliaemoe povysheniem aktivnosti markirovannykh fermentov.

A study was made of the effect of opioid peptides, (Leu)-enkephalin and its synthetic analog dalargin, on the maturation speed (differentiation) and proliferation activity of glioma C-6 cells. This effect on phenotypes of glioma C-6 cells was determined using some biochemical parameters: changes in the activity of glutamine synthetase (astrocytic marker) and cyclic nucleotide phosphorohydrolase (oligodendrocytic marker) in the culture of glioma C-6 cells in the early and late passages. The biochemical analysis was made at the Laboratory in Denver, USA, and we thank Prof. A. Vernadakis for the possibility to carry out a part of this work that helped us to find the growth activity of opioid peptides on the C-6 cells. Proliferation was examined in cultivation conditions approximately conforming the conditions of cultivation for the primary glial cell cultures. The control proliferation level was high in this case. It is demonstrated that opioid peptides accelerate (or strengthen) the expression of phenotypic signs in C-6 glioma cells in early and late passages changing specific activity of the marker enzymes, i.e. operating as a growth factor. Opioid peptides show glial growth factor characteristics on the glioma C-6 glial cell model as well, for glioma C-6 is known to be a perfect model to analyse the action of different substances on the glia.

[The effect of the synthetic leu-enkephalin analog dalargin on the proliferative activity of glioma C6 cells and on the intensity of their DNA synthesis]. / Issledovanie vliianiia sinteticheskogo analoga lei-énkefalina dalargina na proliferativnuiu aktivnost' kletok gliomy C6 i intensivnost' sinteza v nikh DNK.

Effect of dalargin, an opioid peptide (a synthetic analogue of Leu-enkephalin), on proliferation and intensity of DNA synthesis of C6 glioma cells was studied. Specific conditions of cultivation were selected, with a low control value of proliferation, which permitted to assess growth-stimulating effect of the peptide. Growth curves were plotted to assess peptide activity, which demonstrated that reaction was a many-phase process: a significant increase in cell number under peptide effect was observed only at the beginning of the logarithm phase and at the beginning of the prestationary phase of the growth curve. Cell number increased on average by 25-27% in the presence of dalargin as compared to control. Reaction of glioma DNA synthesis to dalargin also demonstrates complexity of the process: the peptide changes DNA synthesis, but as a rule, this process has a three-phase character and is not directly associated with the duration of cultivation in the presence of dalargin. Effect of naloxone, an opiate receptor blocker, was analysed to assess the receptor mechanism. It was found that reaction for naloxone and for combined effect of naloxone and dalargin was not the same.