Résumé
Nonconfluent fibroblasts are relatively depolarized when compared with confluent fibroblasts, and transient hyperpolarizations result from a range of external stimuli as well as internal cellular activities. This electrical activity ceases, along with growth and mitogenic activity, when the cells become confluent. A calcium-activated potassium conductance is thought to be responsible for these hyperpolarizations, but in human fibroblasts the large calcium-activated potassium channel is not stretch-activated. We report here the identification of single stretch-activated cation channels in human fibroblasts, using the cell-attached and inside-out patch clamp techniques. The most prominent channel had a conductance of approximately 60 pS (picoSeimens) in 140 mM potassium and was permeable to potassium and sodium. The channel showed significant adaptation of activity when stretch was maintained over a period of several seconds, but a static component persisted for much longer periods. Higher conductance channels were also observed in a few excised patches.
| Langue d'origine | English |
|---|---|
| Pages (de-à) | 187-190 |
| Nombre de pages | 4 |
| Journal | Biophysical Journal |
| Volume | 54 |
| Numéro de publication | 1 |
| DOI | |
| Statut de publication | Published - 1988 |
| Publié à l'externe | Oui |
Note bibliographique
Funding Information:Stretch-activated channels with similar conductances and selectivity have been reported in several preparations (Guharay and Sachs, 1984; Cooper et al., 1986; Sigurdson et al., 1987) but this channel is novel in exhibiting adapta- tion, as well as sustained activity, in response to suction. It also seems different to stretch-activated channels of lower conductance (Christensen, 1987; Lansman et al., 1987). It has been suggested that other stretch-activated channels are involved in the detection of mechanical stress or cell volume changes. The role of this stretch-activated channel in cell function is unclear, but its high sodium permeability suggests that channel stimulation would cause depolariza- tion. Increases in intracellular sodium (Binggeli and Wein- stein, 1986) and calcium (Okada et al., 1986) are central to two current theories describing activity and membrane potential changes in nonconfluent fibroblasts. Mechanically-activated channels permeant to sodium could, either directly or indirectly, provide the transduction mechanism required for these processes. The location of these stretch-activated channels at the cell border, where continual movements are taking place, suggests that they are likely to be involved in stress measurement due to cell movement, rather than volume regulation. This work was supported by grants from the Medical Research Council of Canada and the Alberta Heritage Foundation for Medical Research. Receivedfor publication 10 February 1988. REFERENCES Binggeli, R., and R. C. Weinstein. 1986. Membrane potentials and ion channels: hypotheses for growth regulation and cancer formation based on sodium channels and gap junctions. J. Theor. Biol. 123:377-401.
ASJC Scopus Subject Areas
- Biophysics