[Effect of stretch on the contractile response of isolated portal vein smooth muscle].

The character of spontaneous activity of the isolated preparation was shown to be affected only by the first stretching stimulus which was due to release of the intracellular Ca. Active contractile responses to stretching at the peak of the contracture due to perfusion of the preparations with the Krebs sodiumless solution, are directly correlated with the speed of the stretching. Stretching of the preparations in calciumless solution elicited no active response.