A conditionally immortalized epithelial cell line for studies of intestinal drug transport

A new cell culture model that better mimics the permeability of the human s mall intestine was developed for studies of passive drug transport. The int estinal epithelial cell line, 2/4/A1, conditionally immortalized with a tem perature-sensitive mutant of the growth-promoting oncogene simian virus 40 (SV40) large T, was grown on permeable supports. The cells grew at 33 degre es C, where the oncogene is fully active, but stopped growing;and entered a differentiation program at 39 degrees C, where the oncogene is inactive. S ignificant cell death was observed at 39 degrees C and, therefore, growth c onditions under which 2/4/A1 cells survive during the differentiation proce ss were developed. Cells grown on extracellular matrices which contained la minin at an intermediate temperature of 37 degrees C formed viable differen tiated monolayers with tight junctions,an increased expression of brush bor der enzymes, and a paracellular permeability that was comparable to that of the human small intestine. The permeability of 17 structurally diverse dru gs gave a sigmoidal relationship with the absorbed fraction of the drugs af ter oral administration to humans. The relationship was compared with those obtained with the well established Caco-2 model and after in vivo perfusio n of the human jejunum. The transport of drugs with low permeability in 2/4 /A1 monolayers was comparable to that in the human jejunum, and up to 300 t imes faster than that in Caco-2 monolayers. The transport of drugs with hig h permeability was comparable in all models. These results indicate that 2/ 4/A1 monolayers ave promising alternatives to Caco-2 monolayers for studies of passive drug transport.