Transcellular transport of 4-iodo-L-meta-tyrosine via system L across monolayers of kidney epithelial cell line LLC-PK1.

The substance 4-[(125)I]iodo-L-meta-tyrosin (4-[(125)I]mTyr) is a radioiodinated amino acid that exhibits high in vivo stability and rapid renal elimination in vivo. We investigated transport of 4-[(125)I]mTyr in LLC-PK(1) (porcine kidney epithelial cell line) monolayers grown on collagen-coated, micro-porous membrane filters. We found that 4-[(125)I]mTyr transport in LLC-PK(1) cells was carrier-mediated and sodium-independent, and that 4-[(125)I]mTyr transport was similar to that of L-Tyr and 3-iodo-alpha-methyl-L-tyrosine. The results of the inhibition experiments suggest that 4-[(125)I]mTyr transport is predominantly mediated by a L-type amino acid transporter 1-like porcine homologue (a component of system L) in both basolateral and apical membrane.