Changes in internal pH caused by movement of fatty acids into and out of clonal pancreatic beta-cells (HIT).
Cells require a constant influx of free fatty acids for lipid resynthesis and metabolic energy. Fatty acids also act as second messengers and modulate channel activities. In the pancreatic beta-cell, fatty acids have both acute and chronic effects on insulin secretion. We show that the addition of fatty acid to pancreatic beta-cells in vitro produces a persistent decrease in intracellular pH, which begins immediately after the addition of fatty acid and has an exponential time course with t1/2 approximately 60 s. The pH drop can be largely reversed by the addition of albumin. The observed pH effect can be explained by passive diffusion ("flip-flop") of un-ionized fatty acid across the plasma membrane. Acidification by a fatty acid dimer and alkalinization by an alkylamine also favor the flip-flop mechanism of transport rather than a protein-mediated mechanism. Our method provides for the first time a real-time measurement of fatty acid import into cells. The significant pH change may be important in mediating some of the regulatory effects of fatty acid, such as inhibition of glycolysis.
Hamilton
J A
JA
Biophysics Department, Boston University School of Medicine, Massachusetts 02118.
Civelek
V N
VN
Kamp
F
F
Tornheim
K
K
Corkey
B E
BE
D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002999:Clone Cells; D005227:Fatty Acids / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007515:Islets of Langerhans / Q000378:metabolism*; D008051:Lipid Bilayers; D010743:Phospholipids / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000378:metabolism
D005227:Fatty Acids; D008051:Lipid Bilayers; D010743:Phospholipids; D012710:Serum Albumin, Bovine