Five new insulin-producing cell lines with differing secretory properties

Five cell lines have been derived from a rat transplantable islet cell tumour using two different methods. The lines differ in morphology and contain and release different amounts of insulin and glucagon (insulin content, 1-90 pmol/10(6) cells; insulin release, 6-250 pmol/10(6) cells per 24 h; glucagon content, less than 0.005-35 pmol/10(6) cells; glucagon release, less than 0.05-10 pmol/10(6) cells per 24 h). All the lines responded to the presence of the secretagogues leucine (20 mmol/l) plus theophylline (5 mmol/l) by increasing the rate of release of insulin approximately twofold. A high extracellular concentration of potassium (40 mmol/l) caused a three- to tenfold calcium-dependent increase in release of insulin and a parallel release of glucagon. Increasing the concentration of glucose from 2.8 to 16.7 mmol/l did not alter the rate of insulin release by any of the cell lines.