An In Vitro Model of the Blood-Brain Barrier: The Response of Madin-Darby Canine Kidney Cells to Triethyl Tin

Abstract

The development of a cell culture model which simulates the properties of the blood–brain barrier (BBB) is necessary for the detection of neurotoxic chemicals that can disrupt the barrier, and to provide a more “risk relevant” in vitro screening battery. The present study evaluates the Madin-Darby canine kidney (MDCK) epithelial cell line for this purpose. Changes in electrical resistance and enzyme activities were correlated in confluent MDCK cells exposed to the neurotoxic metal, triethyl tin (TET). Concentrations of TET (0.001–10μM) were established that produced depression in electrical resistance of the MDCK cells after exposure for 8 hours or caused fluorescein leakage after exposure for 72 hours. Confluent cultures of MDCK cells were then exposed to these concentrations of TET and assayed after exposure for 24 hours and 72 hours for changes in those enzymes common to both epithelial and cerebral endothelial cells. The results indicated that increased alkaline phosphatase (APP), γ-glutamyl transpeptidase (GGTP) and superoxide dismutase (SOD) characterised the loss of electrical resistance and permeability disruption in TET-exposed MDCK confluent cultures. Relative increases in APP and decreases in GGTP activities preceded cytotoxicity, which was associated with a high SOD activity. Such enzyme changes may be predictive endpoints of barrier cell disruption by neurotoxic metals in this cell line and support the additional evaluation of the MDCK cell line as an in vitro “screen” for chemicals that disrupt the BBB.