High-potassium induced contracture in guinea pig ureter

Some characteristic properties of guinea pig ureter in high-K induced contracture were studied. The contracture was composed of three contraction components, quick-phasic, slow transient, and substained states. The height of the second component decreased with time when the preparation was immersed in high-K solution. This was observed during a brief washing treatment with normal Tyrode solution applied at varius times after immersion in high-K solution. When the brief washing treatment was applied after 30 min, a contracture composed of the first and the third components was observed. Similar results were obtained in Ca-induced contracture of K-depolarized preparations. Fluctuations of tension were observed in the course of the contracture. The fluctuations could be evoked by various types treatments and were observed to have some relationship to extracellular Ca. It was indicated that extracellular Ca has an important role in the initiation of each component of the contracture and that the role of Ca is controlled by the cell membrane.