Differential expression of facilitative glucose transporters GLUT1 and GLUT3 in the lens

To determine the expression patterns for members of the facilitative glucose transporter family (GLUT1-4) in the rat lens.

An initial molecular profiling of GLUT expression in lens fiber cells was achieved using reverse transcription-polymerase chain reaction (RT-PCR). The presence of isoform-specific transcript detected by RT-PCR was then confirmed using northern blot analysis and in situ hybridization. The presence of transporter protein was verified by western blot analysis and immunocytochemistry.

Transcripts for GLUT1 and GLUT3, but not for GLUT2 and GLUT4, were detected by RT-PCR of fiber cell mRNA. Transcript for GLUT3, but not for GLUT1, was detected by northern blot analysis of fiber cell total RNA, indicating that GLUT3 was the predominant isoform in the fiber cells. In situ hybridization and immunolocalization in rat lens sections confirmed this result at the transcript and protein levels, respectively. In contrast, GLUT1 was predominantly expressed in the lens epithelium and only to a limited extent in the equatorial fiber cells.

GLUT1 and GLUT3 are differentially expressed in the rat lens. The presence of the high-affinity transporter GLUT3 in fiber cells indicates that these cells have the capacity to take up glucose independently from the epithelium.