Abstract
It is well known that different species have different susceptibilities to ocular diseases, and that in terrestrial mammals, mucins in the tear film are vital to protection of the ocular surface against pathogenic invasion and other challenges. An understanding of the differences in mucin content of marine mammal ocular secretions would be helpful in determining the basis for predisposition to ocular disease. In this study, we compared the carbohydrate profile of tears from two species of cetaceans and three species of pinnipeds as a preliminary step to identifying the types of mucins present. These profiles were also compared to those of human tears. Protein and carbohydrate concentrations of tears, which were collected with IRB & ACUC approvals, from dolphins, seals, sea lions, and humans, were determined using the bicinchoninic and phenol-sulfuric acid methods respectively. Monosaccharides were released from tear samples using acid hydrolysis. Samples were incubated at 100°C for 4.5 hours with a final concentration of 2N trifluoroacetic acid and then subjected to high performance anion exchange chromatography (HPAEC) on a Dionex CarboPac PA-20 column using isocratic gradient elution. Results indicate that carbohydrate to protein ratios differ across species, and HPAEC profiles of hydrolyzed monosaccharides released from tear samples revealed distinct, species-specific chromatographic patterns. Overall, the chromatograms of tears from pinnipeds were the most similar to humans, with each species having a distinct profile. Differences in carbohydrate profiles across species are likely to indicate variations in mucin composition of tears. Of interest, it has been observed that the tears of the two dolphin species examined are much more viscous than those of pinnipeds, and this may correlate with different mucin composition. We hypothesize that tear film mucin composition will correlate with species-specific differences in vulnerability to ocular surface disease.
Acknowledgements
We thank the staff and trainers at Dolphin Quest Oahu, Oahu, HI; Golfworld Marine Park, Panama City Beach, FL; Aquarium of Niagara, Niagara Falls, NY; and New England Aquarium, Boston, MA, for their very generous support in collecting marine mammal tear samples for this project; and David A. Sullivan, Schepens Eye Research Institute and Massachusetts Eye and Ear, Boston, MA, for advice. Grant Support: NIH EY014847 (PA) & R01EY05612; Arey's Pond Boat Yard, S. Orleans, MA
* Presenting author