TOXICOLOGICAL AND ABSORPTION ENHANCING EFFECTS OF GLYCOFUROL-75 AND SODIUM GLYCOCHOLATE IN MONOLAYERS OF HUMAN INTESTINAL EPITHELIAL (CACO-2) CELLS

The effects of glycofurol 75 (GF) and sodium glycocholate (GC) on the toxicity and permeability of the human intestinal cell line Caco-2 wer e studied. The intracellular dehydrogenase activity of the cells was u sed as a measure of the toxicity. Concentrations of GC from approx. 10 mM inhibited the intracellular dehydrogenase activity and above 40 mM the activity was less than 10% of the initial level. The concentratio ns resulting in 50% inhibition (IC50) were 24.2 mM (1.2%) and 380 mM ( 6.8%) for GC and GF respectively. GF concentrations of less than 100 m M did not affect the activity. The effects of GF and GC on the absorpt ion of the hydrophilic marker molecule [C-14]mannitol were studied at concentration levels corresponding to no (23.7 mM GF and 5.1 mM GC), a bout 25% (117 mM GF and 17.2 mM GC) and 50% (380 mM GF and 24.2 mM GC) inhibition in dehydrogenase activity. The apparent permeability coeff icient for mannitol in control monolayers was 5.7 x 10(-8) cm/s. 5.1 m M GC did not enhance the permeability, whereas 17.2 and 24.2 mM enhanc ed it significantly (p < 0.001). GF (380 mM) did not enhance the perme ability. The apparent permeability coefficient of insulin in control m onolayers was less-than-or-equal-to 9.8 x 10(-8) cm/s, but varied cons iderably. 24.2 mM GC enhanced the P(app) significantly (p < 0.001), wh ereas GF (380 mM) did not affect the absorption of insulin. The Caco-2 cells were studied by transmission electron microscopy after exposure to 380 mM GF for 1 h. Cells exposed to a mannitol solution of the sam e osmolality as 380 mM GF (about 700 mosm) and untreated monolayers of Caco-2 cells served as controls. GF caused morphological alteration o f the epithelial cells resulting in a distorted appearance with disord ered microvilli, disorganized terminal web and intracellular vacuols. This effect is problaby due to the high osmolality as the cells expose d to mannitol displayed the same distorted appearance. However, no eff ect could be observed on the integrity of the apical cell membrane and the tight junctions.