The function of SLC22A2 (solute carrier family 22 member 2, ENSG00000112499) is as follows. Electrogenic voltage-dependent uniporter that mediates the transport of a variety of organic cations such as endogenous bioactive amines, cationic drugs and xenobiotics (PubMed:9260930, PubMed:9687576). Functions as a Na(+)-independent, bidirectional uniporter (PubMed:21128598, PubMed:9687576). Cation cellular uptake or release is driven by the electrochemical potential, i.e. membrane potential and concentration gradient (PubMed:15212162, PubMed:9260930, PubMed:9687576). However, may also engage electroneutral cation exchange when saturating concentrations of cation substrates are reached (By similarity). Predominantly expressed at the basolateral membrane of hepatocytes and proximal tubules and involved in the uptake and disposition of cationic compounds by hepatic and renal clearance from the blood flow (PubMed:15783073). Implicated in monoamine neurotransmitters uptake such as histamine, dopamine, adrenaline/epinephrine, noradrenaline/norepinephrine, serotonin and tyramine, thereby supporting a physiological role in the central nervous system by regulating interstitial concentrations of neurotransmitters (PubMed:16581093, PubMed:17460754, PubMed:9687576). Also capable of transporting dopaminergic neuromodulators cyclo(his- pro), salsolinol and N-methyl-salsolinol, thereby involved in the maintenance of dopaminergic cell integrity in the central nervous system (PubMed:17460754). Mediates the bidirectional transport of acetylcholine (ACh) at the apical membrane of ciliated cell in airway epithelium, thereby playing a role in luminal release of ACh from bronchial epithelium (PubMed:15817714). Also transports guanidine and endogenous monoamines such as vitamin B1/thiamine, creatinine and N-1- methylnicotinamide (NMN) (PubMed:12089365, PubMed:15212162, PubMed:17072098, PubMed:24961373, PubMed:9260930). Mediates the uptake and efflux of choline (PubMed:9260930). Mediates the bidirectional transport of polyamine agmatine and the uptake of polyamines putrescine and spermidine (PubMed:12538837, PubMed:21128598). Able to transport non-amine endogenous compounds such as prostaglandin E2 (PGE2) and prostaglandin F2-alpha (PGF2-alpha) (PubMed:11907186). Also involved in the uptake of xenobiotic 4-(4-(dimethylamino)styryl)-N-methylpyridinium (ASP) (PubMed:12395288, PubMed:16394027). May contribute to regulate the transport of organic compounds in testis across the blood-testis- barrier (Probable). {ECO:0000250|UniProtKB:Q9R0W2, ECO:0000269|PubMed:11907186, ECO:0000269|PubMed:12089365, ECO:0000269|PubMed:12395288, ECO:0000269|PubMed:12538837, ECO:0000269|PubMed:15212162, ECO:0000269|PubMed:15783073, ECO:0000269|PubMed:15817714, ECO:0000269|PubMed:16394027, ECO:0000269|PubMed:16581093, ECO:0000269|PubMed:17072098, ECO:0000269|PubMed:17460754, ECO:0000269|PubMed:21128598, ECO:0000269|PubMed:24961373, ECO:0000269|PubMed:9260930, ECO:0000269|PubMed:9687576, ECO:0000305|PubMed:35307651}. [Isoform 2]: In contrast with isoform 1, not able to transport guanidine, creatinine, cimetidine and metformin. {ECO:0000269|PubMed:12089365, ECO:0000269|PubMed:15212162, ECO:0000269|PubMed:16272756}.