[Effects of amixine on electrophoretic mobility of murine T lymphocytes].

The amixine-induced early changes in the electrophoretic mobility (EPM) of murine splenic T lymphocytes were studied in vitro by the microelectrophoresis technique. It has been found that T lymphocytes treated with amixine have a greater EPM within the first hours of amixine addition than control cells. This change in EPM depends on the concentration of amixine in the medium and the duration ofamixine exposure. It was concluded that the amixine-treated cells have a greater net negative surface charge density than control cells. This effect may play an important role in the cell-cell interaction during the immune response.

[Alterations in ATP-dependence of swelling-activated Cl- current associated with neuroendocrine differentiation of LNCaP human prostate cancer epithelial cells].

Increasing population of malignant, apoptosis resistant neuroendocrine (NE) cells due to differentiation of prostate epithelial/basal cells is a hallmark of advanced, androgen-independent prostate cancer, for which there is no successful therapy. Acquisition of apoptosis resistance involves alterations in the mechanisms of cell volume homeostasis, of which volume-regulate anion channels (VRAC) that carry swelling-activated Cl- current (I(Cl,swell)) represent one of the key determinants. Given that VRAC function is generally known to be ATP-dependent, here we investigated how such dependence may evolve during NE differentiation of LNCaP prostate cancer epithelial cells. In the whole-cell patch-clamp recording mode I(Cl,swell) could be activated in response to hypotonicity-induced cell swelling in control and NE-differentiated (by incubation in membrane-permeable cAMP analogs) LNCaP cells even following total depletion of intracellular ATP using a cocktail of metabolic inhibitors. However, this basal I(Cl,swell) had about 30% higher density and was less inactivating in NE-differentiated cells. Inclusion of 5 mM Mg-ATP in the patch pipette caused I(Cl,swell) augmentation in both cell types. The augmentation in the control cells was more prominent and occurred mostly at the expense of a non-inactivating current component. We conclude that I(Cl,swell) in LNCaP cells consists of a non-inactivating, ATP-dependent and inactivating, ATP-independent components. NE differentiation promotes the increase of non-inactivating component and partial loss of its ATP sensitivity making the whole I(Cl,swell) less ATP-sensitive as well. By largely avoiding the ATP metabolic control I(Cl,swell) may contribute to better control of cell volume under metabolic stress and thus enhance the survival rates of apoptosis-resistant NE cells.

[Adenosine triphosphate-dependence of volume sensitive chloride current in LNCaP cell line of human prostate cancer].

Although sensitivity to intracellular ATP is considered to be one of the hallmarks of swelling activated Cl- current (I(Cl,swell)) involved in regulatory volume decrease (RVD) following hypotonic stress, the type and manner of such sensitivity seems to vary in different cell types. Here by using whole-cell patch-clamp recording we investigated ATP sensitivity of I(Cl,swell) in LNCaP human prostate cancer cell line. Suppression of endogenous ATP production with metabolic inhibitors (oligomycin, iodoacetate and rotenone) during cell dialysis with ATP- and Mg2+-free pipette solution did not prevent I(Cl,swell) in response to hypotonic exposure. However, supplementing this solution with 5 mM Na-ATP led to the development of I(Cl,swell) with nearly 305 higher density and less pronounced voltage-dependent inactivation (manifested mainly by the increase of non-inactivated current component) at positive potentials. On the contrary, inclusion of 1 mM Mg2+ in the patch pipette resulted in even smaller I(Cl,swell) (30% lower density compared to Mg2+-free conditions), which inactivated completely on prolonged depolarization. The presence of 5 mM Mg-ATP in the pipette did not affect I(Cl,swell) density. Neither intervention significantly altered the rate of I(Cl,swell) development in response to hypotonicity. We conclude that intracellular ATP, a positive modulator of I(Cl,swell)-carrying volume-regulated anion channel (VRAC) in LNCaP cells most likely acts via binding rather than hydrolysis and/or phosphorylation reactions, whereas intracellular Mg2+ is VRAC inhibitor.

[Changes in extracellular K+ concentration modulate properties of voltage dependent K+ channel conductance in PC-12 cells]. / Proiavy plastychnosti potentsialkerovanoï kaliievoï providnosti klityn PC-12 pry zminakh zovnishn'oklitynnoï kontsentratsiï K+.

The complex processing and integration of signals observed in neurons are facilitated by the diverse range of gating properties of the ion channels in this cell type, particularly the voltage-gated K+ channels (Kv). A distinctive combination of K+ channels endows neurons with a broad repertoire of excitable properties and allows each neuron to respond in a specific manner to a given input at a given time. The properties of many K+ channels can be modulated by second messenger pathways activated by neurotransmitters and other stimuli. K+ channels are among the most frequent targets of the actions of several signalling systems.

[Effect of neuroendocrine cell differentiation of the human prostatic neoplasm cell line LNCaP on the characteristics of volume-sensitive chloride content]. / Vplyv neiroendokrynnoho dyferentsiiuvannia klityn raku prostaty liudyny liniï LNCaP na kharakterystyky ob'iemchutlyvoho khlornoho strumu.

By means of patch-clamp technique we examined changes in volume-regulated chloride current (ICl,swell) at neuroendocrine differentiation of androgen-dependent LNCaP prostate cancer cells. In those cells with neuroendocrine differentiation resulted from an increase in the intracellular cAMP, ICl,swell became much faster in response to applying external hypotonic solution and cell swelling. Changes in final rectification and voltage-dependent inactivation were not detected, as compared to the control cells. The differentiation also diminished ICl,swell blockade by Ca2+ transported via store-operated channels (SOC). On the base of our data we suggest that potentiation of the current at neuroendocrine differentiation, at least in part, resulted from a decrease in an inhibitory effect of Ca2+, transported into a cell through SOC, on volume-sensitive chloride current. Accelerated current in those cells might be induced by cytoskeleton rearrangement at the neuron-like growth.