Unperturbed islet α-cell function examined in mouse pancreas tissue slices

Non-technical summary Critical investigation into pancreatic islet alpha-cell biology in health and diabetes has been sparse and inconsistent because of technical difficulties in islet isolation and dispersion into single cells. We have circumvented these difficulties by employing the pancreas slice preparation. We functionally characterized (electrophysiologically) the alpha-cells in their in situ native state, then loaded the tested cells with biocytin dye to subsequently confirm the cell identities by immunocytochemistry. We characterized a very large number of alpha-cells, which showed a wide-range distribution in the electrophysiological parameters of several ion channels (ATP-sensitive K+, Na+ and Ca2+ currents) and capacitance changes as measure of exocytosis of glucagon granules. This could explain the apparent inconsistency of previous reports on alpha-cells that inadvertently showed skewed data due to insufficient sampling of alpha-cells. Our innovative approaches will enable future studies into elucidating alpha-cell dysregulation in diabetes.Critical investigation into alpha-cell biology in health and diabetes has been sparse and at times inconsistent because of the technical difficulties with employing conventional strategies of isolated islets and dispersed single cells. An acute pancreas slice preparation was developed to overcome the enzymatic and mechanical perturbations inherent in conventional islet cell isolation procedures. This preparation preserves intra-islet cellular communication and islet architecture in their in situ native state. alpha-Cells within tissue slices were directly assessed by patch pipette and electrophysiologically characterized. The identity of the patched cells was confirmed by biocytin dye labelling and immunocytochemistry. alpha-Cells in mouse pancreas slices exhibited well-described features of I-Na (excitable at physiological membrane potential), I-KATP, small cell size, low resting membrane conductance, and inducible low and high voltage-activated I-Ca, the latter correlating with exocytosis determined by capacitance measurements. In contrast to previous reports, our large unbiased sampling of alpha-cells revealed a wide range distribution of all of these parameters, including the amount of K-ATP conductance, Na+ and Ca2+ current amplitudes, and capacitance changes induced by a train of depolarization pulses. The proposed pancreas slice preparation in combination with standard patch-clamping technique allowed large sampling and rapid assessment of alpha-cells, which revealed a wide distribution in alpha-cell ion channel properties. This specific feature explains the apparent inconsistency of previous reports on these alpha-cell ion channel properties. Our innovative approach will enable future studies into elucidating islet alpha-cell dysregulation occurring during diabetes.