Table 1.

Properties of mammalian ENT2 proteins.

ENT2 transporter	Gene location	Amino acid	Tissue distribution	Permeant selectivity
hENT2	11q13.2	456	Ubiquitous	Purine and pyrimidine nucleoside and nucleobases
mENT2	19; 19 A	456	Brain, NG108-15 cells [7]	Purine and pyrimidine nucleoside and adenine
rENT2	1q43	456	Intestine, brain, epididymis [7]	Purine and pyrimidine nucleoside and nucleobases except cytosine
rbENT2	Un	456	nd	Purine and pyrimidine nucleoside and hypoxanthine

Mammalian ENT2 proteins differ in the distributions and their abilities to transport some nucleobases. h: human; m: mouse; r: rat; rb: rabbit; Un: unplaced; nd: not determined.