[Relation between the labeling index and thymidine incorporation in cultured islands of Langerhans of the rat: stimulation of DNA synthesis by EGF-S3].

DNA synthesis and labelling index of isolated neonatal rat islets were investigated during a 4 to 5 culture period in TCM 199 (10 mmol/l glucose) under selected conditions, as change of serum concentration in the medium or addition of a proliferation stimulating fraction. Additionally it should be proved whether the DNA-synthesis of pancreatic islets, measured as [3H]-thymidine incorporation, is representative for the amount of cells during the S-phase (= "growth fraction"). There is a correlation between the incorporation of [3H]-thymidine into the TCA-precipitate and the labelling index of islets determined on HE-stained radioautographs. For this reason and because of being less time-consuming, the measurement of DNA synthesis is a suitable screening method for selection of factors increasing the growth fraction of pancreatic beta-cells. Only the addition of FGF-S3 (growth stimulating raw prepared isolated from bovine brain) during culture caused a significant increase of DNA synthesis and labelling index of the islets. The labelling index of radioautographs stained by immunofluorescence method for insulin did not differ significantly from that determined at HE-stained radioautographs. Insulin secretion and content of the islets were not influenced by the addition of FGF-S3.