Two types of stretch-activated channel activities in guinea-pig gastric smooth muscle cells.

Using cell-attached patch-clamp techniques, stretch-activated channels were investigated in guinea-pig gastric smooth muscle cells. Suction applied to the pipette interior or cell swelling induced by hypotonic bath solution induced two kinds of channel openings, a short-lasting and small opening (OS) and a long-lasting and large opening (OL) with conductances of 33 and 53 pS, respectively. Threshold suction for OS was lower than that for OL. In many patches examined, OS and OL coexisted. The distributions of open- and closed-times of OS could be fitted by the sum of two exponentials, the time constants of which were 1.3 and 9.3 ms for the open-time, and 0.6 and 8.4 ms for the closed-time. Both OS and OL were blocked by 100 microM Gd3+ in the pipette. The reversal potentials did not change upon altering [Cl-]o. The results indicate that OS and OL seem to represent non-selective cation channel activities, which do not discriminate among K+, Na+, and Ca2+. These channels may play an important role in the stretch-induced contraction in gastric muscle.