STRETCH ACTIVATION OF A TOAD SMOOTH-MUSCLE K-ACIDS( CHANNEL MAY BE MEDIATED BY FATTY)

1. Using standard single channel patch clamp techniques we studied the stretch sensitivity of a 20 pS K+-selective channel which is activate d by fatty acids and found in freshly dissociated smooth muscle cells from the stomach of the toad Bufo marinus. 2. A pulse of suction appli ed to the back of the patch pipette in order to stretch the membrane r esulted in activation of this K+ channel. A train of suction pulses re sulted in a gradually increased level of channel activity during each successive pulse, as well as an increase in baseline activity between pulses. This pattern contrasts markedly with many other stretch-activa ted channels whose activation is limited to the duration of the suctio n pulse. 3. Application of fatty acids augmented the response to stret ch. In contrast, application of 10 mu M defatted albumin, which remove s fatty acids from membranes, rapidly and reversibly decreased the res ponse to stretch. 4. These results are consistent with the hypothesis that fatty acids which are generated by mechanical stimuli, perhaps by mechanically activated phospholipases, are the intermediaries in acti vation of certain mechanically sensitive ion channels.