Fig. 3.

Glucose-stimulated ATP/ADP, IP₇ and insulin release are compromised in islets from diabetic ob/ob mice. (A) ATP/ADP, (B) IP₇ and (C) insulin secretion in response to stimulation with 16.7 mM glucose for 3 min, in pancreatic islets obtained from diabetic ob/ob mice and age-matched lean male mice. Data are presented as a percentage of unstimulated control. (D) Comparison of basal levels of ATP/ADP, IP₇ and insulin secretion in lean vs. ob/ob islets. Using data derived from experiments depicted in (A–C) we normalized all the data to inositol lipids to demonstrate the relationship between the basal levels of ATP/ADP, IP₇ and insulin secretion in islets from either lean or ob/ob mice. There is a close association between the levels of these three parameters. All bars and plots are means ± SEM, from 3 to 4 independent experiments, *p < 0.05, **p < 0.01, Student's t-test. (E) Proportion of β-cells in islets isolated from ob/ob and lean mice at the age of 3 months. The analysis of insulin expressing cells by FACS shows that the relative proportion of β-cells over the total islet cells is not significantly different (Student's t-test) between ob/ob (n = 5) and lean (n = 4) islet preparations. Data are expressed as means ± SEM. (F) Initial rates of IP6K activity of cell lysates from lean (n = 3) and ob/ob (n = 4) islet preparations, means ± SEM. The activity is not significantly different (Student's t-test).