Functions as a polyspecific organic cation transporter, efficiently transporting many organic cations such as monoamine neurotransmitters 1-methyl-4-phenylpyridinium and biogenic amines including serotonin, dopamine, norepinephrine and epinephrine. May play a role in regulating central nervous system homeostasis of monoamine neurotransmitters. May be involved in luminal transport of organic cations in the kidney and seems to use luminal proton gradient to drive organic cation reabsorption. Does not seem to transport nucleoside and nucleoside analogs such as uridine, cytidine, thymidine, adenosine, inosine, guanosine, and azidothymidine. In (PubMed:16873718) adenosine is efficiently transported but in a fashion highly sensitive to extracellular pH, with maximal activity in the pH range 5.5 to 6.5. Glu-206 is essential for the cation selectivity and may function as the charge sensor for cationic substrates. Transport is chloride and sodium-independent but appears to be sensitive to changes in membrane potential. Weakly inhibited by the classical inhibitors of equilibrative nucleoside transport, dipyridamole, dilazep, and nitrobenzylthioinosine. May play a role in the regulation of extracellular adenosine concentrations in cardiac tissues, in particular during ischemia. Located to the plasma membranes of ventricular myocytes and vascular endothelial cells. Targeted to the apical membranes of differentiated kidney epithelial cells. Expressed abundantly in the heart, in both cardiomyocytes and vascular endothelial cells (at protein level). Highly expressed in brain, kidney and skeletal muscle. In the brain expressed in cerebellum, cerebral cortex, medulla, occipital pole, frontal and temporal lobes putamen and in the spinal cord. Lower expression in liver, pancreas, and liver. Expressed in endometrial tissue, exclusively in the stroma. Expression is high in the proliferative phase, decreases during the secretory phase, and is no longer detectable in the menstrual phase. N-glycosylated. Belongs to the SLC29A/ENT transporter (TC 2.A.57) family.