Objectives: The use of primary human β-cells for studying Ca signaling is limited by the scarcity of human pancreatic islets. Rodent insulinoma cell lines are widely used, but it is difficult to extrapolate results obtained from rodent cells to human. Recently, a genetically engineered human β-cell line EndoC-BH1 has been developed. We have examined whether the EndoC-BH1 cells could be used as a model for studying Ca signaling in the β-cells.
Methods: We used microscope-based fluorometry to measure cytoplasmic-free Ca concentration from fura-2-loaded single EndoC-BH1 cells cultured on glass cover slips. Ca responses to different agonists of insulin secretion were studied. Insulin secretion was measured by radioimmunoassay.
Results: EndoC-BH1 cells secreted insulin in response to glucose in a dose-dependent manner, and the secretion was enhanced by GLP-1 (glucagon-like peptide 1). Glucose, potassium chloride, carbachol, L-arginine, and tolbutamide increased cytoplasmic-free Ca concentration in the EndoC-BH1 cells. We found that GLP-1 was essential for Ca response to glucose and tolbutamide.
Conclusions: We concluded that the EndoC-BH1 cells can be used as model cells to study Ca signaling and stimulus-secretion coupling in the human β-cells.