TERTIARY AMMONIUM ION INDUCES CONSTRICTIO NS OF RAT AORTA SEGMENTS AND INCREASES THE MOBILITY OF LIPIDS IN THE MEMBRANE OF RAT AORTA SMOOTH-MUSCLE CELLS

The effects of tertiary ammonium ion - IEM-1194 (decyldiiosopropylammo nium bromide) - on smooth muscle cells (SMC) isolated from rat aorta w ere investigated. Using the patch-clamp technique in the cell-attached mode, two types of effects on the Ca2+-activated K+ channels were rec orded after application of IEM-1194: an increase in the number of fast transition bursts in open channels and prolongation of the burst. The removal of the agonist led to the activation of these channels. Mecha nical responses of aortic rings were recorded using the method of isom etric tension measurements. IEM-1194 (100-400 mu M) caused constrictio ns consisting of two periods. The first period emerged immediately aft er application of the agonist. The second one was observed 10-15 munit es after application. The constriction period of aorta was followed by the dilation period that lasted more than 1,5 hours. The same results were obtained in the Ca2+-free external solution. Measurementst of th e SMC membrane fluidity by the method of spin probes demonstrated that TEM-1194 induced an increase in mobility of membrane lipids. Based on these results, the mechanism of the IEM-1194 action on the Ca2+-activ ated K+ channels was suggested.