title: Transport of carnitine and acetylcarnitine by carnitine/organic cation transporter (OCTN) 2 and OCTN3 into epididymal spermatozoa.
abstract: Carnitine and acetylcarnitine are important for the acquisition of motility and maturation of spermatozoa in the epididymis. In this study, we examined the involvement of carnitine/organic cation transporter (OCTN) in carnitine and acetylcarnitine transport in epididymal spermatozoa of mice. Uptake of both compounds by epididymal spermatozoa was time-dependent and partially Na(+)-dependent. Kinetic analyses revealed the presence of a high-affinity transport system in the spermatozoa, with K(m) values of 23.6 and 6.57 muM for carnitine and acetylcarnitine respectively in the presence of Na(+). Expression of OCTN2 and OCTN3 in epididymal spermatozoa was confirmed by immunofluorescence analysis. The involvement of these two transporters in carnitine and acetylcarnitine transport was supported by a selective inhibition study. We conclude that both Na(+)-dependent and -independent carnitine transporters, OCTN2 and OCTN3, mediate the supply of carnitine and acetylcarnitine to epididymal spermatozoa in mice.
authors.affiliation: Division of Pharmaceutical Sciences, Department of Molecular Biopharmaceutics, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kobayashi
authors.forename: Ikumi
authors.initials: I
authors.lastname: Tamai
authors.forename: Yoshimichi
authors.initials: Y
authors.lastname: Sai
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yoshida
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Wakayama
authors.forename: Yasuto
authors.initials: Y
authors.lastname: Kido
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Nezu
authors.forename: Shoichi
authors.initials: S
authors.lastname: Iseki
authors.forename: Akira
authors.initials: A
authors.lastname: Tsuji
mesh_terms: D000108:Acetylcarnitine / Q000493:pharmacokinetics*; D000818:Animals; D001622:Betaine / Q000031:analogs & derivatives / Q000494:pharmacology; D001693:Biological Transport, Active; D002331:Carnitine / Q000493:pharmacokinetics* / Q000494:pharmacology; D004822:Epididymis; D005455:Fluorescent Antibody Technique; D008297:Male; D008565:Membrane Proteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051379:Mice; D027701:Organic Cation Transport Proteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011738:Pyrilamine / Q000494:pharmacology; D000074058:Solute Carrier Family 22 Member 5; D013079:Sperm Maturation / Q000502:physiology; D013081:Sperm Motility / Q000502:physiology; D013094:Spermatozoa / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D027701:Organic Cation Transport Proteins; C498687:Slc22a21 protein, mouse; C492019:Slc22a5 protein, mouse; D000074058:Solute Carrier Family 22 Member 5; D001622:Betaine; C002889:gamma-butyrobetaine; D000108:Acetylcarnitine; D011738:Pyrilamine; D002331:Carnitine