1999 Volume 14 Issue supplement Pages 106-107
We recently developed the retinal capillary endothelial cell lines (TR-iBRB) from transgenic rat harboring temperature-sensitive SV 40 large T-antigen gene. The purpose of the present study is to characterize the transport functions such as L-cystine and L-lactate as are substrates for system xc and MCT, respectively, in TR-iBRB cells. TR-iBRB expressed P-glycoprotein encoded mdrl aand 1 b mRNA. RT-PCR analysis revealed MCT1 and MCT2 mRNA in TR-iBRB. The uptake of [14C]-L-lactate was a pH-dependent, temperature-dependent, and concentration-dependent manner with a Michaelis constant (Km) of 1.7 mM. It was inhibited by monocarboxylates but not by dicarboxylates. The uptake of [14C]-L-cystine by TR-iBRB was a concentration-dependent mannerwith a Km of 9.2μM. It was inhibited by substrates orinhibitors of system xc such as L-glutamic acid, L-α-aminoadipic acid, L-homocysteic acid, and L-quisqualic acid, but not by Laspartic acid, neutral and basic amino acids. L-Cystine uptake was increased by diethyl malete (DEM) treatment. L-Cystine uptake increased by DEM was inhibited by substrates and inhibitors of system xc, suggesting induction of system xc in TR-iBRB. Pending in vivo analysis, TR-iBRB is a useful in vitro model to elucidate transport functions at iBRB. These transport functions in iBRB may contribute the regulation of pharmacokinetics in retina.
