The influence of acetoacetate and butyrate on calcium influx and ATP concentrations in HT-29 cells

The effects of acetoacetate and butyrate on Ca2+-influx in HT-29 cells were unknown. Extracellular signals can be transferred to the intracellular environment of the cell via changes in the Ca2+-concentration. Extracellular Ca2+ may enter the cell via Ca2+-channels in the plasma membrane. Physiological processes occurring within the cell are dependent on Ca2+-concentration, including enzyme activity. Intracellular Ca2+-concentrations were measured using Fura-2/AM, a fluorescent intracellular Ca2+-probe. Ca2+-concentrations were measured immediately on application of the inducers to the cells, as well as after a 9 day incubation period. The effect of these inducers on the L-type voltage-operated Ca2+-channels were determined using the whole-cell patch-clamp technique. To validate these results for the intestinal epithelial model, membrane current studies were performed on HT-29 cells grown on a polycarbonate membrane. ATP concentrations were measured, and the theoretical effect of the inducers on PDE 4 activity was determined. It was found that both acetoacetate and butyrate blocked Ca2+-influx through the L-type voltage-operated Ca2+-channels, resulting in the initial low Ca2+-concentration (p < 0.05). The blockage effect is short-lived as after a 9 day incubation period in the presence of the inducers, Ca2+-concentrations were higher than that of the HT-29 control sample (p < 0.05). ATP concentrations of the cells were decreased in the presence of the inducers (p < 0.05), whilst it was suggested that no interaction between the catalytic site of PDE 4 and the inducers existed.