1. β-Cell function in human islets derived from a number of kidney donors was investigated by using various types of islet preparations.
2. With fresh islets, both insulin release and biosynthesis were increased by raising glucose concentrations, although the response was a variable one.
3. In fresh islets, the effects of 5 mmol of glucose/l on release were potentiated by 10 mmol of d-3-hydroxybutyrate/l.
4. Insulin release at 20 mmol of glucose/l was inhibited by adrenaline (0.1 mmol/l), and potentiated by theophylline (10 mmol/l) in the presence of 5 mmol of glucose/l, in islets cultured for 4 days.
5. After culture for 8 days, islets still showed an increase in insulin release and biosynthesis in response to glucose.
6. Pancreas slices derived from fresh human tissue also responded to increasing concentrations of glucose with a sigmoidal curve for insulin release.