Expression and characterization of lacrimal gland water channels in Xenopus oocytes.

Lacrimal glands transport fluid for secretion as tears. To examine whether the expression of the aquaporin family of water channels is essential for water transport in lacrimal glands, we determined the water permeability in Xenopus oocytes injected with rat lacrimal gland poly(A)+ RNA. In oocytes injected with poly(A)+ RNA, osmotic water permeability was 4-fold higher than that observed in vehicle-injected controls. The enhanced water permeability was inhibited by 65% by coinjection of poly(A)+ RNA with antisense aquaporin-5 but not antisense aquaporin-1 oligonucleotide. To detect aquaporin mRNA in rat lacrimal glands, we performed reverse transcription-polymerase chain reaction analysis. PCR products were detected using specific aquaporin-5 primers. Our results strongly suggest that rat lacrimal glands express aquaporin-5 water channels for lacrimation.