Fig. 3

Hormonal secretion in response to low or high external glucose concentration in vitro. Glucose challenge was performed by incubating the cells with low-glucose buffer (2 mM) or high-glucose buffer (25 mM) for 4 h. a Insulin secretion in response to high glucose in vitro. b Glucagon secretion in response to low glucose in vitro. n = 3. *Significant p < 0.05 (Student’s t test)