Propionate activates multiple ion transport mechanisms in the HT29-18-C1 human colon cell line
Rowe, W.A.; Blackmon, D.L.; Montrose, M.H.
American Journal of Physiology 265(3 Pt 1): G564-G571
1993
ISSN/ISBN: 0002-9513 PMID: 8214077 Document Number: 422138
Short-chain fatty acids (SCFAs) are the major solutes and the major anions in the colonic lumen. We studied the response of suspended HT29-18-C-1 cells (an epithelial cell line derived from a human colon carcinoma) to SCFA exposure. Cellular response was evaluated by measurement of cell volume (Coulter counter), intracellular pH (pH-i; measured fluorometrically with 2',7'-bis(2-carboxymethyl)-5-(6)-carboxyfluorescein (BCECF)), and intracellular Na+, K+, and Cl- content (flame photometry and chloride titrator). Exposure to 130 mM propionate in isosmotic medium causes a rapid decrease in pH-i and activates pH-i recovery via amiloride-sensitive Na-H exchange. In the presence of propionate, Na-H exchange also causes cell swelling to a peak volume 11% above control cells and causes a 2.8-fold increase in intracellular Na+ content. After peak swelling, a regulatory volume decrease (RVD) significantly reduced volume and intracellular Na+ returned to baseline. Other SCFAs (acetate, butyrate, and valerate) also elicit swelling and RVD. Activation of the Na+-K+-adenosinetriphosphatase (ATPase) is required to return Na+ to normal levels and to indirectly provide ion gradients required for propionate-induced RVD, but Na+K+-ATPase activity does not directly mediate RVD. When 1 mM 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) is added in the presence of propionate, RVD was inhibited and cell Na+ content increased. Cl- depletion inhibited propionate-induced RVD and diminished the effect of SITS. Under identical gradient conditions, SITS had no effect on Cl-flux in either the presence or absence of propionate, suggesting an indirect Cl- requirement, In summary, exposure of cultured colonocytes to propionate activates multiple ion transporters responsible for net cation uptake, recovery of pH-i, and recovery from swelling.