A cell perifusion system of isolated rat islets for studies on rapid insulin-glucose dynamics

We have developed a cell perifusion system of isolated rat islets, to improve the accuracy of controlling the medium content and the stability of the medium flow. This new system presents the following characteristics: (1) There is always a consistent flow in the perifusion chamber and only half of its volume is altered when switching the medium. (2) The medium containing test substances can be prepared and held ready in very close proximity to islets. The test glucose media are introduced to the islets immediately after a switch. (3) The environment of the islets could be repeatedly changed from one state to another in a rigorous stepwise manner. The system can provide an accurate switch of glucose concentrations both in time and quantity without introducing pressure disturbances, which makes a suitable tool for studies on rapid insulin-glucose dynamics. In experiments of perifused rat islets, our results further confirmed the observation that the amplitudes of oscillatory insulin secretions were magnified when glucose levels increased but their periods were unaffected. In addition, insulin secretions instantly increased in response to the sudden increase of glucose levels, but gradually decreased in response to the sudden decrease of glucose levels.