High affinity carnitine transporter; the uptake is partially sodium-ion dependent. Thought to mediate the L-carnitine secretion mechanism from testis epididymal epithelium into the lumen which is involved in the maturation of spermatozoa. Also transports organic cations such as tetraethylammonium (TEA) and doxorubicin. The uptake of TEA is inhibited by various organic cations. The uptake of doxorubicin is sodium-independent. Detected in the plasma membrane of Sertoli cells and in the luminal membrane of epithelial cells in the epididymis. Widely expressed at low levels in adult tissues and fetal brain, lung, liver and kidney. Expressed in testis and epididymis (at protein level). Expressed at lower levels in bone marrow and fetal liver. Expressed in hematopoietic cells, including CD34(+) leukocytes and leukemia cells. Abundantly expressed in ovarian cancer clear-cell adenocarcinoma. Expressed in endometrium (at protein level); highly expressed during the normal secretory phase, but expression is significantly reduced in the proliferative phase. Belongs to the major facilitator (TC 2.A.1) superfamily. Organic cation transporter (TC 2.A.1.19) family.