title: Transepithelial transport in cell culture: bioenergetics of Na-, D-glucose-coupled transport.
abstract: The renal cell line LLC-PK1 cotransports Na and D-glucose from the apical to the basolateral side of the cell monolayer, and the short-circuit current (Isc) measures the net amount of Na transported. Under conditions of maximal cotransport, the addition of phlorizin or removal of Na reversibly decreased oxygen consumption by one-half. In the absence of glycolytic substrates, alpha-methyl-D-glucoside stimulated Isc and oxygen consumption, although the Isc came to a steady state 50% less than when glycolytic substrates were present. The addition of other aerobic substrates did not increase Isc; however, when non-cotransported glycolytic substrates were introduced the Isc returned to a maximum with an associated fall in oxygen consumption and increased lactate production. Thus, in the absence of glycolytic substrates aerobic ATP formation may be rate-limiting for Na, D-glucose cotransport. For this epithelium glycolysis makes an important contribution to the provision of energy for transport. Oxygen consumption does not correlate well with Isc and is not a good measure of the energy used in transport.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D002478:Cells, Cultured; D004848:Epithelium / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis; D007668:Kidney; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption; D010695:Phlorhizin / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D013552:Swine
chemical_list: D012964:Sodium; D010695:Phlorhizin; D005947:Glucose