Denervation of rabbit lacrimal gland increases levels of transferrin and unidentified tear proteins of 44 and 36 kDa.

PURPOSE

The main lacrimal gland secretes proteins and fluid that make up the aqueous component of the tears. Previous reports indicate that the parasympathetic innervation of the gland influences the secretion of protein from the lacrimal gland. We investigated the effect of lacrimal nerve transection on the levels of individual proteins and overall protein concentration in the tear fluid.

METHODS

The main lacrimal gland was unilaterally denervated in adult rabbits at the site of nerve entry to the gland. The contralateral gland (sham-operated) had identical surgical manipulations, excluding nerve transection. Tears were collected daily from both eyes for up to 9 days, after which lacrimal glands were collected. SDS-PAGE, densitometric and image analysis, and Western blot were performed.

RESULTS

Consistently measurable tear protein bands ranged from 6 kDa to 85 kDa, using densitometric analysis. Lacrimal gland denervation produced a sustained increase in proteins of 85, 44, and 36 kDa in tears and lacrimal gland tissue from the denervated side, compared with the sham-operated side (0.025 > p > 0.001). The band at 85 kDa was identified as transferrin by Western blot. Tears from the denervated glands also showed transient decreases in low molecular weight tear proteins (18, 12/10, and 6 kDa), as well as a decrease in overall protein concentration, compared with tears from sham-operated glands and non-operated glands (p < 0.001).

CONCLUSIONS

These results demonstrate that, in rabbit tears, the quantities of transferrin and two unidentified tear proteins, as well as overall protein concentration, are influenced by the sensory and/or autonomic innervation to the lacrimal gland. The decrease in overall tear protein concentration after lacrimal gland denervation may be related to a loss of nerve-regulated secretagogue-induced protein secretion.