PI3-Kinase-dependent electrogenic intestinal transport of glucose and amino acids

Intestinal glucose and amino acid transport is stimulated by the serum- and glucocorticoid-inducible kinase isoforms SGK1, SGK2, and SGK3 and protein kinase B which are, in turn, stimulated following activation of the phosphoinositol-3 kinase (PI3 kinase). The present study has been performed to explore whether pharmacological inhibition of the PI3 kinase affects electrogenic jejunal transport of glucose and amino acids. In Ussing chamber experiments, glucose (20 mM), phenylalanine (20 mM), glutamine (20 mM), cysteine (20 mM), and proline (20 mM) generated lumen negative currents (I _glc, I _phe, I _gln, I _cys, and I _pro), respectively, which gradually declined following application of the PI3 kinase inhibitor Wortmannin (1 μM). Within 40 min, Wortmannin treatment significantly decreased I _glc by 39 ± 10% (n = 5), I _phe by 70 ± 7% (n = 4), I _gln by 69 ± 8% (n = 4), I _cys by 67 ± 8% (n = 6), and I _prol by 79 ± 12% (n = 3). A similar decline of I _glc was observed following application of the PI3 kinase inhibitor LY294002 (50 μM). Exposure to the inhibitors did not significantly alter transepithelial potential difference and resistance in the absence of substrates for electrogenic transport. The observations suggest that the electrogenic transport of glucose and several amino acids requires the continued activity of PI3 kinase. R. Rexhepaj and F. Artunc shared first authorship.