Functional Expression of Carnitine/Organic Cation Transporter 1 in Murine Choroid Plexus

Biol Pharm Bull. 2024;47(9):1484-1486. doi: 10.1248/bpb.b24-00451.

Abstract

Membrane transporters expressed in the choroid plexus (CP) are involved in the transport of substances between the blood and cerebrospinal fluid (CSF). Carnitine/organic cation transporter 1 (OCTN1, also known as SLC22A4) is expressed in rodent CP; however, its specific roles in blood-CSF transport remain unclear. Therefore, in this study, we aimed to evaluate the potential role of OCTN1 in the elimination of substances from CSF. Tritium-labeled ergothioneine ([3H]ERGO), a typical in vivo substrate of OCTN1, was injected into the lateral ventricles of wild-type and octn1 gene knockout (octn1-/-) mice. Clearance of [3H]ERGO from CSF was higher than that of the bulk flow marker, [14C]mannitol, in wild-type mice. However, [3H]ERGO clearance was significantly lower in octn1-/- mice than in wild-type mice. Furthermore, OCTN1 expression in CP was determined via immunohistochemical analysis. CP/CSF ratio of [3H]ERGO was significantly lower in octn1-/- mice than in wild-type mice. These results suggest that OCTN1 is functionally expressed in CP and involved in the elimination of ERGO from CSF in mice.

Keywords: blood–cerebrospinal fluid barrier; choroid plexus; ergothioneine; organic cation transporter 1.

MeSH terms

  • Animals
  • Choroid Plexus* / metabolism
  • Ergothioneine* / cerebrospinal fluid
  • Ergothioneine* / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout*
  • Organic Cation Transport Proteins* / genetics
  • Organic Cation Transport Proteins* / metabolism
  • Symporters

Substances

  • Slc22a4 protein, mouse
  • Organic Cation Transport Proteins
  • Ergothioneine
  • Symporters