INSULIN AND IGF-1 RECEPTORS IN A HUMAN INTESTINAL ADENOCARCINOMA CELL-LINE (CACO-2) - REGULATION OF NA-TRANSPORT ACROSS THE BRUSH-BORDER( GLUCOSE)

Both insulin and IGF-1 receptors are present in intestinal mucosal cel ls, although their role in this tissue is unclear. We have characteriz ed these receptors in a human adenocarcinoma cell line, Caco-2, and ex amined their role in the regulation of glucose transport and absorptio n in these cells. The Caco-2 cells demonstrated specific insulin and I GF-1 receptors. They also bound cytochalasin B, suggesting the presenc e of a glucose transporter-like protein. When grown on membranes, the Caco-2 cells formed columnar, bipolar cells with tight junctions. The monolayer selectively transported D-glucose and methyl-D-glucose, with complete exclusion of L-glucose, D-mannitol and inulin. The absorptio n of glucose across the monolayer occurred via a Na+/glucose cotranspo rter, as indicated by a change in short circuit current after addition of glucose to the apical membrane. When examined under several condit ions, neither insulin nor IGF-1 had an affect on the transport of gluc ose across the Caco-2 monolayer, nor the production of lactate by the cells. It is concluded that the insulin and IGF-1 receptors of Caco-2 cells do not regulate glucose transport.