Influence of growth factors on an insulin-producing cell line (RINm5F)

The influence of IGF-I, insulin and epidermal growth factor (EGF) as well as glucose as control was studied on both growth and function of RINm5F cells, an insulin-producing cell line derived from rat insulinoma tissue. 3H]thymidine incorporation and DNA content (fluorometrically) were measured for estimating cell growth, insulin release and biosynthesis ( 3H]leucine incorporation) as parameters for cell function. There was a significant increase in both 3H] thymidine incorporation and DNA content into RIMm5F cells by glucose already at very low concentrations. IGF-I and high concentrations of insulin too were able to stimulate cell growth (insulin also in additional experiments with isolated rat islets). EGF, however, was without growth effect on this cell line (in contrast to previous own results in isolated islets). Insulin secretion and biosynthesis were also increased by very low glucose concentrations. IGF-I and EGF were ineffective regarding these functional parameters in RINm5F cells. Besides for glucose, our results demonstrate a role for IGF-I and insulin, but not for EGF, in regulating growth of these cells.