|Budget Amount *help
¥3,100,000 (Direct Cost : ¥3,100,000)
Fiscal Year 1998 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1997 : ¥2,100,000 (Direct Cost : ¥2,100,000)
Effects of phalloidin and cytochalasin B or D were investigated on the activities of the ATP-sensitive K channels in the rabbit portal vein isolated by collagenase using whole-cell voltage-clamp and single channel current recording methods. When cytochalasin D (20muM) were applied in the pipette, the maximum amplitude of the pinacidil (100muM) -induced current was not changed by cytochalasin D (in the presence of cytochalasin, 95*74pA ; in the absence of cytochalasin, 97*59 ; n=22). However, when mean values of the maximum amplitudes of the pin acidil-induced current obtained from the same animal were compared, the amplitude of the pinacidil-induced current was always smaller in cytochalasin-treated cells than in untreated cells (60*40% ; n=22). In 3 out of 6 cells, cytochalasin D (20muM) reduced the amplitude of the pinacidil-induced current, when cytochalasin was simultaneously applied in the superfusate. However, no change was observed by application of cytochalasin D in the rest of cells. On the other hand, extracellularly application of phalloidin (20muM) increased the pinacidil-induced current in 4 out of 12 cells, reduced the current in 2 out of 12 cells. No change was seen in other cells by extracellularly application of phalloidin. Phalloidin (10muM) did not change the activity of the single channel current induced by pinacidil observed in cell-attached condition. A 'run-down' phenomenon, recorded by the membrane excision, was not prevented by phalloidin. Furthermore, phalloidin did not change the activity of the single channel currents induced by pinacidil with GDP in the inside-out membrane patch condition. Cytochalasin B and cytochalasin D inhibit neither amplitude nor mean open time of the single channel current. These results indicated that cytoskeletons in the rabbit portal vein might not participate the modulation on the channel activity of the ATP-sensitive K channels, in comparison to the ATP-sensitive channels in the cardiac celk.