Organ culture of fetal mouse pancreas. The effect of culture conditions on insulin and glucagon secretion.

Seventeen-day-old mouse pancreas was grown in organ culture under various culture conditions and the insulin released into the medium, either chronically or during acute incubations, was measured. Three media, DME, RPMI 1640, and TC199, were tested, each at glucose concentrations of 1, 2, 3, and 4 g/L. Fetal pancreata maintained in RPMI 1640 at 4 g/L glucose secreted the most insulin over a 25-day period. Tissue grown in RPMI 1640 and DME secreted more insulin in higher glucose concentrations, but explants grown in TC199 secreted low levels of insulin regardless of glucose concentration. Fetal pancreata grown in medium supplemented with 5% FCS secreted less insulin in acute incubations than tissues grown in 10%, 15%, 20%, or 30% FCS, which secreted equivalent amounts. There was no difference in the amount of insulin released by islets grown in media supplemented with 15% FCS from four different batches. Although fetal islets grown in high glucose concentrations generally secreted more insulin (and less glucagon) than “normoglycemic” controls, their ability to release insulin in subsequent acute incubations was impaired. Explants, which had been maintained for 2 wk in 2.5 or 4 g/L glucose and a further 3 days in normoglycemic medium, secreted less insulin and glucagon in acute release exeriments than tissue maintained in 1 g/L glucose throughout. Light microscopy of cultured fetal pancreas showed that tissue remained viable at all glucose concentrations tested and differences in response could not be attributed to selective necrosis. Tranplantation of cultured islets indicated that tissue grown under normoglycemic conditions functioned better than tissue grown in hyperglycemic media.