Cx36-Mediated Coupling Reduces β-Cell Heterogeneity, Confines the Stimulating Glucose Concentration Range, and Affects Insulin Release Kinetics
Open Access
- 1 April 2007
- journal article
- Published by American Diabetes Association in Diabetes
- Vol. 56 (4), 1078-1086
- https://doi.org/10.2337/db06-0232
Abstract
We studied the effect of gap junctional coupling on the excitability of β-cells in slices of pancreas, which provide a normal environment for islet cells. The electrophysiological properties of β-cells from mice (C57Bl/6 background) lacking the gap junction protein connexin36 (Cx36−/−) were compared with heterozygous (Cx36+/−) and wild-type littermates (Cx36+/+) and with frequently used wild-type NMRI mice. Most electrophysiological characteristics of β-cells were found to be unchanged after the knockout of Cx36, except the density of Ca2+ channels, which was increased in uncoupled cells. With closed ATP-sensitive K+ (KATP) channels, the electrically coupled β-cells of Cx36+/+ and Cx36+/− mice were hyperpolarized by the membrane potential of adjacent, inactive cells. Additionally, the hyperpolarization of one β-cell could attenuate or even stop the electrical activity of nearby coupled cells. In contrast, β-cells of Cx36−/− littermates with blocked KATP channels rapidly depolarized and exhibited a continuous electrical activity. Absence of electrical coupling modified the electrophysiological properties of β-cells consistent with the reported increase in basal insulin release and altered the switch on/off response of β-cells during an acute drop of the glucose concentration. Our data indicate an important role for Cx36-gap junctions in modulating stimulation threshold and kinetics of insulin release.Keywords
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