Abstract
The periodontal ligament fibroblasts (PDL fibroblasts), the principal cells in PDL, are responsible for PDL functions. In this work, we examined the properties of mechanosensitive TREK-1 K+ channels (a member of the two-pore-domain K+ channel family) in cultured human PDL fibroblasts. Single-channel currents of TREK-1 channels were recorded by patch-clamp single-channel-recording techniques. The single-channel conductance of TREK-1 channel was 100 pS in symmetrical K+-rich solutions. The open probability of the channel was low at the quiescent state (Po=0.012±0.004, n=44), but it was strongly increased by the application of membrane stretch. Unsaturated fatty acids, including arachidonic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, oleic acid, DHA, and EPA dose-dependently enhanced the channel activity (Po=0.247±0.069 by 10 μM arachidonic acid, n=8), but saturated fatty acids, such as palmitic acid, stearic acid, and arachidic acid had no effects. The channel activity was also increased by acid solution (Po=0.211±0.036 at pH 6.0, n=7), and temperature (Po=0.072±0.043 at 50°C, n=3). The channel activity, which had been enhanced by 10 μM arachidonic acid, was decreased by the application of catalytic subunit of protein kinase A at 20 U/ml (Po=0.028±0.018, n=3). The channel was partially blocked by quinine, quinidine, and Ba2+, but was not affected by tetraethylammonium, Cs+, and 4-aminopyridine. Immunocytochemical observation showed that TREK-1 K+ channel proteins were present in PDL fibroblasts. [Jpn J Physiol 55 Suppl:S71 (2005)]
