Pertusa, José A GLeón-Quinto, TrinidadBerná, GenovevaTejedo, Juan RHmadcha, AbdelkrimBedoya, Francisco JMartín, FranzSoria, Bernat2023-01-252023-01-252017-11-03http://hdl.handle.net/10668/11765β-cells release hexameric Zn2+-insulin into the extracellular space, but monomeric Zn2+-free insulin appears to be the only biologically active form. The mechanisms implicated in dissociation of the hexamer remain unclear, but they seem to be Zn2+ concentration-dependent. In this study, we investigate the influence of albumin binding to Zn2+ on Zn2+-insulin dissociation into Zn2+-free insulin and its physiological, methodological and therapeutic relevance. Glucose and K+-induced insulin release were analyzed in isolated mouse islets by static incubation and perifusion experiments in the presence and absence of albumin and Zn2+ chelators. Insulin tolerance tests were performed in rats using different insulin solutions with and without Zn2+ and/or albumin. Albumin-free buffer does not alter quantification by RIA of Zn2+-free insulin but strongly affects RIA measurements of Zn2+-insulin. In contrast, accurate determination of Zn2+-insulin was obtained only when bovine serum albumin or Zn2+ chelators were present in the assay buffer solution. Albumin and Zn2+ chelators do not modify insulin release but do affect insulin determination. Preincubation with albumin or Zn2+ chelators promotes the conversion of "slow" Zn2+-insulin into "fast" insulin. Consequently, insulin diffusion from large islets is ameliorated in the presence of Zn2+ chelators. These observations support the notion that the Zn2+-binding properties of albumin improve the dissociation of Zn2+-insulin into subunits after exocytosis, which may be useful in insulin determination, insulin pharmacokinetic assays and islet transplantation.enAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/AnimalsBlood GlucoseChelating AgentsExocytosisInsulinIslets of LangerhansMaleMiceRadioimmunoassayRatsRats, WistarSerum AlbuminZincresearch article29099856open access10.1371/journal.pone.01875471932-6203PMC5669427https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0187547&type=printablehttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC5669427/pdf