The Influence of Tear Proteins on the Film Stability of Rabbit Tear Extracts

Abstract

This study was undertaken to gain an understanding of the significance of tear proteins in stabilizing the tear film. Either a sigma agonist, N,N-dimethyl-2-phenylethylamine HCl (AF2975), or a sigma antagonist, haloperidol, was administered to rabbit eyes in order to increase or decrease protein secretion, respectively. At 0, 10 and 60 minutes after instillation, tear proteins were extracted from Schirmer strips and measured for total protein. A portion of the extract was used for separating five major protein fractions using size-exclusion HPLC. Total protein extract or individual protein fractions were measured for surface tension by the horizontal capillary method and for in vitro break up time (in vitro BUT), a newly designed procedure. A statistically significant decrease was measured for surface tension and a concomitant increase was measured for in vitro BUT for the total protein samples at 10 and 60 minutes after instillation of AF2975 compared to the vehicle treated eye. The results for haloperidol yielded an increase in surface tension and an decrease in in vitro BUT. When the tear proteins were separated into five major fractions, only the 23 minute protein fraction was found to decrease surface tension and increase in vitro BUT following AF2975 administration. Haloperidol, a sigma antagonist, showed an exact opposite effect for the total protein and the 23 minute protein fraction.

Divalent Cations in Tears, and Their Influence on Tear Film Stability in Humans and Rabbits

“…NITBUT was used as an indicator of surface tension, as a negative correlation has been found previously between surface tension and NITBUT in normal and dry eye patients. 26,27 In our study the normal ionic components of rabbit and human tears also were analyzed and compared.…”

Lacritin and the tear proteome as natural replacement therapy for dry eye

“…By scavenging lipids, tear lipocalin is thought to help clear the ocular surface of sloughed cellular debris from epithelial turnover that might interfere with wetting. It also stabilizes the tear film (Schoenwald et al, 1998), and with ligand is itself stabilized (Tsukamoto et al, 2009). …”

Effects of Topical Fucosyl-Lactose, a Milk Oligosaccharide, on Dry Eye Model: An Example of Nutraceutical Candidate

“…Atropine’s action is related to a pharmacological antagonism to muscarinic receptors in the lacrimal gland that cause a significant decrease of aqueous production with an evident modification of tear stability. It has been described ( Stern et al, 1998 ) that ocular surface (cornea, conjunctiva, and accessory lacrimal glands), Meibomian glands, and main lacrimal gland, are interconnected by neural reflex loops that maintain an integrated “functional unit.” The neural reflex loops involved in maintaining the normal tear physiology can be blocked by anticholinergic agents such as atropine, as demonstrated by Schoenwald et al (1998) in a rabbit dry eye model.…”