Vitamin D in Tear Fluid.

Area of Science:

• Ophthalmology
• Endocrinology
• Molecular Biology

Background:

• Vitamin D is crucial for various bodily functions.
• The presence and source of vitamin D in tear fluid remain largely uncharacterized.
• Lacrimal and Harderian glands are responsible for tear production.

Purpose of the Study:

• To identify the sources of vitamin D in tear fluid.
• To investigate the expression of endocytic proteins, megalin and cubilin, in lacrimal and Harderian glands.
• To explore the role of these proteins in vitamin D transport into tears.

Main Methods:

• Utilized wild-type, heterozygous, and vitamin D receptor (VDR) knockout mice.
• Analyzed megalin and cubilin expression in lacrimal and Harderian glands using RT-PCR, Western blot, and immunohistochemistry.
• Measured vitamin D levels in lacrimal and accessory gland fluid of rabbits via mass spectroscopy.

Main Results:

• VDR knockout mice exhibited reduced megalin and cubilin expression.
• Immunohistochemistry revealed megalin presence in apical duct cells, with decreased staining in VDR knockout mice.
• Vitamin D2 was more abundant than vitamin D3 in rabbit tear fluid, with higher concentrations in gland fluid compared to plasma.

Conclusions:

• This study first demonstrates the presence of megalin and cubilin in the glands that produce tear fluid.
• The findings support the hypothesis that megalin and cubilin play a role in the secretion of vitamin D into tear fluid via duct cells.