Role of actin microfilament in hyposmotic membrane stretch-induced increase in muscarinic current of guinea-pig gastric myocytes.

To investigate the relationship between cytoskeleton and hyposmotic membrane stretch-induced increase in muscarinic current, the role of actin microfilament in hyposmotic membrane stretch-induced increase in muscarinic current was studied with the whole-cell patch clamp technique in guinea-pig gastric myocytes. In this study, the muscarinic current was induced by carbachol (50 micromol/L) or GTPgammaS (0.5 mmol/L). The results showed that hyposmotic superfusate (202 mOsmol/L) increased carbachol-induced current (I(CCh)) by 145+/-27% and increased GTPgammaS-induced current by 183+/-30%; but in the presence of cytochalasin-B (Cyt-B, 20 micromol/L), an actin cytoskeleton disruptor, hyposmotic membrane stretch increased I(CCh) by 70+/-6%. However, hyposmotic membrane stretch induced increase in I(CCh) was potentiated to 545+/-81% by phalloidin (20 micromol/L), an actin microfilament stabilizer. The results demonstrated that hyposmotic membrane stretch increased the muscarinic currents induced by carbachol or GTPgammaS and that the actin microfilament is involved in the process in guinea-pig gastric myocytes.