Characterization of ion channels seen in subconfluent human dermal fibroblasts.

Abstract

SUMMARY1. Ion channels expressed in human dermal fibroblasts are characterized using the patch-clamp technique.2. A number of different ion channels were found but their expression occurred at various frequencies. The most commonly found phenotype was the expression of voltage-gated K+ current. This 'typical' K+ current was seen in about 60% of the cells recorded.3. Subtypes of voltage-gated K+ channels could be discerned by differences in gating kinetics. One has fast inactivation and resembles the 'A' K+ current. Additional subtypes were sometimes discerned based on activation kinetics.4. The large-conductance Ca2+-activated K+ channel (maxi-K+) could be found in nearly every cell but required large depolarizations to activate using the standard Ca2l-buffered pipette solution (10-8 M [Ca2+]i).5. Inward rectifier K+ channels were seen in a low percentage of cells. The inward rectifier K+ current was sensitive to 'wash-out' if guanosine 5'-O-(3-thiotriphosphate) (GTPyS) was included in the pipette solution dialysing the cell.6. Tetrodotoxin (TTX)-sensitive voltage-gated Na+ channels were seen but in a lower number of cells recorded, about 20 %. Evidence for subtypes of Na+ channels were sometimes seen based on differences in gating kinetics.7. An ATP-dependent osmotically activated Cl-current was also found. This current showed some outward rectification but was otherwise voltage independent.8. In addition, a cell-to-cell contact-associated K+ current was described. This current was linear over the voltage ranges used and whose gating correlated with the existence of gap junctions.9. These currents were characterized to determine the baseline behaviour of unstimulated cells and to compare to bradykinin-stimulated cells described in the following paper. As unexcitable cells, human dermal fibroblasts are capable of expressing a surprising diversity of ion channel phenotypes and of ion channel modulations.

β-Subunits of voltage-gated sodium channels in human prostate cancer: quantitative in vitro and in vivo analyses of mRNA expression

“…In such a situation, any epithelial cell-specific VGSC-expression changes with CaP in vivo would be hard to detect, especially if the non-epithelial cell types present in prostate (for example, smooth muscle cells, peripheral nerves, fibroblasts) also expressed significant levels of VGSCs, which is very likely. [36][37][38][39] Indeed, although not statistically significant, median fold-changes in vivo (non-CaP vs CaP) did appear to correlate very well with corresponding in vitro changes (between strongly and weakly metastatic cells), as shown in Figure 5. In particular, (a) the direction of the change is the same for b1 (increased with disease progression in vitro and in vivo) and b4 (decreased with disease progression), and (b) the magnitude of the in vivo change for b1 and b4 is consistent with the B50-fold 'dilution' of the in vitro change observed previously for Na v 1.7.…”

A small-conductance Ca2+-activated K+ current and Cl- current in rat dental pulp cells.

“…Therefore, it would be interesting to relate actions of these sensory neuropeptides and chemical mediators to the modulation of K ‫ם‬ and Cl ‫מ‬ conductances in dental pulp cells. As described in a wide variety of cells, ion channels can be involved in the signal codes for proliferation, secretion of extracellular matrix proteins and cell differentiation 8,11,20,22) as well as the intercellular electrical/chemical communications through gap junctions 2,3,8,9,19,21,24,28) . The K ‫ם‬ and Cl ‫מ‬ channels expressed in dental pulp cells are most likely responsible for cellular functions underlying dental pulp metabolisms.…”

“…Ionic channels in the plasma membranes of a wide variety of cells play important roles in cellular functions such as the secretion of extracellular matrix proteins, regulation of bone tissue metabolism and cell proliferation 8,15,30) . Recent studies using patch-clamp recording techniques in tissue-cultured cells derived from human dental pulp have demonstrated the presence of a high-conductance Ca ‫ם2‬ -activated K ‫ם‬ current 5) and a tetrodotoxinsensitive voltage-dependent Na ‫ם‬ current 6) .…”

Acute electrophysiological responses of bradykinin‐stimulated human fibroblasts.

“…Cell preparation and solutions and reagents were as described in the previous paper (Estacion, 1991).…”

“…Human fibroblasts express a diverse repertoire of ion channels (Estacion, 1991) and respond to mitogenic growth factors by generating the second messenger molecules IP3, DG and Ca2"; this suggests that modulation of ion channels may occur in human fibroblasts. There are preliminary reports of modulation of whole-cell currents in response to serum stimulation (Pallotta & Peres, 1989) in human dermal fibroblasts.…”