Effects of zinc during culture of an insulin-producing rat cell line (RINm5F).

The effects of various Zn2+ concentrations on cell proliferation, insulin secretion and contents of insulin and zinc were studied in a clonal cell line (RINm5F) established from a transplantable rat islet tumor. The RINm5F cells were equally effective in proliferating and releasing insulin at zinc concentrations ranging from 0.013 to 0.073 mM. The percentage of cells able to exclude trypan blue was significantly less in cultures with 0.073 mM Zn in the medium. Increasing the extracellular concentrations of Zn2+ to 0.044 and 0.073 mM, respectively, resulted in a 40-60% reduction in the cellular content of insulin. There was a significant increase (73%) in the cellular content of zinc only when increasing the extracellular concentration of the element to 0.073 mM. The addition of 0.2 mM EGTA to a zinc-deficient medium had no effect on proliferation, insulin release or content of insulin and zinc, indicating the presence of a stable endogenous pool of zinc maintaining the function of the RINm5F cells for at least 5 days in culture.