Insulin stimulation of Na+ transport and glucose metabolism in cultured kidney cells

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Abstract
A line of toad kidney cells (A6) in continuous culture was evaluated for ion transport and metabolic responses to insulin. The cells were grown on permeable supports to allow access of the medium to both basolateral and apical sides of the epithelium. Insulin, on the basolateral side only, produced an increase in short-circuit current (Isc) that was maximal at 40-60 min. A concentration-dependent increase in Isc and potential difference (PD) was found in the range of 10-3.2 X 10(3) microunits/ml insulin. The maximal stimulation of Isc and PD was approximately six- and twofold, respectively. After insulin exposure Isc was equivalent to net Na+ transport, indicating active Na+ transport stimulation. Insulin was also found to increase the incorporation of radiolabeled glucose into glycogen. Thus A6 cells exhibit both transepithelial transport and metabolic responses to insulin.