CHANGES IN INTERNAL PH CAUSED BY MOVEMENT OF FATTY-ACIDS INTO AND OUTOF CLONAL PANCREATIC BETA-CELLS (HIT)

Cells require a constant influx of free fatty acids for lipid resynthe sis and metabolic energy. Fatty acids also act as second messengers an d modulate channel activities. In the pancreatic beta-cell, fatty acid s have both acute and chronic effects on insulin secretion. We show th at the addition of fatty acid to pancreatic beta-cells in vitro produc es a persistent decrease in intracellular pH, which begins immediately after the addition of fatty acid and has an exponential time course w ith t(1/2) similar to 60 s. The pH drop can be largely reversed by the addition of albumin. The observed pH effect can be explained by passi ve diffusion (''flip-flop'') of un-ionized fatty acid across the plasm a membrane. Acidification by a fatty acid dimer and alkalinization by an alkylamine also favor the flip-flop mechanism of transport rather t han a protein-mediated mechanism. Our method provides for the first ti me a real-time measurement of fatty acid import into cells. The signif icant pH change may be important in mediating some of the regulatory e ffects of fatty acid, such as inhibition of glycolysis.