title: Glucose induces opposite intracellular Ca2+ concentration oscillatory patterns in identified alpha- and beta-cells within intact human islets of Langerhans.
abstract: 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 Ca(2+) dependent. In the current study, we used confocal microscopy and immunocytochemistry to unequivocally characterize the glucose-induced Ca(2+) signals in alpha- and beta-cells within intact human islets. Extracellular glucose stimulation induced an opposite response in these two cell types. Although the intracellular Ca(2+) concentration ([Ca(2+)](i)) in beta-cells remained stable at low glucose concentrations, alpha-cells exhibited an oscillatory [Ca(2+)](i) response. Conversely, the elevation of extracellular glucose elicited an oscillatory [Ca(2+)](i) pattern in beta-cells but inhibited low-glucose-induced [Ca(2+)](i) signals in alpha-cells. These Ca(2+) 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.
authors.affiliation: Institute of Bioengineering, Miguel Hernandez University, Ctra. N-332, Km. 87, 03550 Sant Joan d'Alacant, Spain. ivanq@umh.es
authors.forename: Ivan
authors.initials: I
authors.lastname: Quesada
authors.forename: Mariana G
authors.initials: MG
authors.lastname: Todorova
authors.forename: Paloma
authors.initials: P
authors.lastname: Alonso-Magdalena
authors.forename: Marta
authors.initials: M
authors.lastname: Beltrá
authors.forename: Everardo M
authors.initials: EM
authors.lastname: Carneiro
authors.forename: Franz
authors.initials: F
authors.lastname: Martin
authors.forename: Angel
authors.initials: A
authors.lastname: Nadal
authors.forename: Bernat
authors.initials: B
authors.lastname: Soria
mesh_terms: D000293:Adolescent; D000328:Adult; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D050416:Glucagon-Secreting Cells / Q000187:drug effects* / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007150:Immunohistochemistry; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism; D018613:Microscopy, Confocal
chemical_list: D005947:Glucose; D002118:Calcium