Effects of phospholipase C on the electrical and mechanical activity of guinea pig taenia coli.

At concentrations ranging from 2 to 5.10-5 phospholipase C (Sigma Chemical Company, St. Louis) induces a sustained contraction of taenia coli. According to the results of the electrophysiological investigations performed by the sucrose gap method, the above effect is associated with membrane depolarization and increase of spike discharge rate. The contraction induced by phospholipase C is entirely dependent on external calcium and not demonstrable on preparations bathed for 3-5 min in a calcium free medium. The calcium induced contraction of taenia coli bathed in a calcium free medium is strongly enhanced by a pretreatment with phospholipase C. At concentrations abolishing the mechanical and the electrical effects of drugs acting by a receptor mechanism (acetylcholine, noradrenaline), phospholipase C does not appreciably affect the responses of taenia coli to BaCl2 or papaverine. The results suggest that membrane phospholipids control electrical properties and calcium movements in taenia coli and play an essential role in the drugs-receptor interaction. © 1977 The Italian Pharmacological Society.