Figure 1.

Insulin granules in the submembrane space of MIN6 cells after beta cell desensitization or rest. (A) Aspect of granulation state and size of insulin-EGFP-labeled MIN6 cells after 18-hour culture in the presence of 500 µM tolbutamide (upper row, left) and control (upper row, right) or in the presence of 1 µM clonidine (lower row, left) and control (lower row, right). Representative images of 52 (desensitization by tolbutamide) or 60 (rest by clonidine) MIN6 cells. (B) Insulin granule number and mobility in the submembrane space of insulin-EGFP-labeled MIN6 cells after culture for 18 hours either in the presence of 500 µM tolbutamide or 1 µM clonidine. The graphs show the number of granules in the first image of a sequence of 200 images (upper left), the cumulative number of granules identified during the entire sequence (upper right), the number of those granules that were present during the entire sequence (long-term residents, lower left) and the lateral mobility (lower right). For each parameter, a significant difference existed between drug exposure and control culture (p˂0.01, unpaired two-sided t-test), except for the granule number in the first image after tolbutamide. Values are means±SEM of 52 (tolbutamide and controls) or 60 (clonidine and controls) cells each.