Glucose induces opposite intracellular ca2+ concentration oscillatory patterns in identified α- and β-cells within intact human islets of langerhans

Homeostasis of blood glucose is mainly regulated by the coordinated secretion of glucagon and insulin from alpha- and beta-cells within the islets of Langerhans. The release of both hormones is Ca2+ dependent. In the current study, we used confocal microscopy and immunocytochemistry to unequivocally characterize the glucose-induced [Ca2+](i) signals in and beta-cells within intact human islets. Extracellular glucose stimulation induced an opposite response in these two cell types. Although the intracellular Ca2+ concentration ([C2+](i)) in beta-cells remained stable at low glucose concentrations, alpha-cells exhibited an oscillatory [Ca2+](i) response. Conversely, the elevation of extracellular glucose elicited an oscillatory [Ca2+] pattern in beta-cells but inhibited low-glucose-induced [Ca2+](i) signals in a-cells. These Ca2+ Signals were synchronic among beta-cells grouped in clusters within the islet, although they were not coordinated among the whole beta-cell population. The response of alpha-cells was totally asynchronic. Therefore, both the alpha- and beta-cell populations within human islets did not work as a syncitium. in response to glucose. A deeper knowledge of alpha- and beta-cell behavior within intact human islets is important to better understand the physiology of the human endocrine pancreas and may be useful to select high-quality islets for transplantation.