Effects of allantoin on insulin secretion and blood glucose in Wistar rats. Plasma glucose was reduced by intravenous (i.v.) injection of allantoin into fasted Wistar rats after glucose (1 g/kg) loading (A). Basal plasma glucose (B) and basal plasma insulin (C) were also influenced by allantoin. Values are indicated as the mean and SEM from each group of eight rats. Vehicle only (0.9% NaCl in distilled water) was given at the same volume. *P < 0.05, **P < 0.01, and ***P < 0.001 versus data from animals treated with vehicle (control).