Glucocorticoids stimulate the division of rat pancreatic islet tumour cells in tissue culture.

The effects of hormones on the growth of beta cells, obtained from an X-ray induced transplantable rat islet cell tumour, were studied in tissue culture. Cells were cultured in Dulbecco's modified medium containing 1% bovine serum albumin, which did not permit fibroblast outgrowth. Among a variety of different hormones tested, the most potent growth promoters were found to be the corticosteroids whose potency was related to their glucocorticoid activity. After 5 weeks in culture with prednisolone (270 nmol/l), all cells stained immunohistochemically for insulin, although the insulin content was decreased to 10% that of fresh cells. Growth hormone (10 micrograms/ml) stimulated DNA replication to a small extent in the presence or absence of glucocorticoids. Insulin secretion from freshly prepared tumour cells was not stimulated by glucose but was increased two- to threefold by leucine (20 mmol/l) plus theophylline (5 mmol/l). This pattern of stimulation was observed still in cells cultured for 4 weeks in prednisolone-supplemented medium.