1987 年 8 巻 4 号 p. 215-223
Acute and long-term effects of glucose on B-cells from an X-ray induced transplantable rat insulinoma were examined in vitro. Fresh tumour cells failed to respond acutely to glucose or glucose plus theophylline with increased 45Ca uptake and insulin release. During culture in RPMI-1640, blood cells and necrotic tumour cells rapidly disappeared. Cultured secretory cells did not proliferate but exhibited >95% viability and consumed substantial amounts of glucose. Glucose (1.4-22.2 mM) did not affect insulin content or insulin release in 7-day cultures, but both parameters decreased by 51% and 80% compared with 2-day cultures. Insulin output represented 1% of the fall in insulin content suggesting substantial cellular insulin degradation. Acute exposure of 2-day cultured cells to 16.7 mM glucose did not affect insulin release (64-88 ng/106 cells/h) or 45Ca uptake (1.4-2.0 nmol/ 106 cells/h). However, combination with 5 mM theophylline evoked a 22-30% stimulatory insulin response. Cells cultured for 7 days also failed to respond acutely to glucose with increased 45Ca uptake, but a 22-34% stimulation of insulin secretion was evident after maintenance at 5.6-22.2 but not 1.4 mM glucose. Addition of theophylline potentiated the insulin response irrespective of a change in 45Ca uptake.