EFFECT OF HIGH GLUCOSE-CONCENTRATION ON PROINSULIN BIOSYNTHESIS AND CONVERSION BY HUMAN ISLETS

In the present study we investigate whether glucose concentration coul d have an effect on proinsulin biosynthesis and processing. We culture d control human islets under chronic high and low glucose concentratio ns. After the culture period, islets were pulse-labeled and chased for different periods of time, Proteins from islets were collected, insul in immunoprecipitated, and analyzed by alkaline-urea gel electrophores is. We have found an accelerated rate of proinsulin conversion by thos e islets exposed to high glucose concentration (at 24.4 mM of glucose) , but not by those islets cultured at low glucose concentration (at 5. 5mM of glucose). However, we do not observe any decrease or increase o n newly proinsulin synthesis in any of these conditions. (C) 1998 Acad emic Press.