Presence of tear lipocalin and other major proteins in lacrimal fluid of rabbits

Identification and isolation of a Fel d 1–like molecule as a major rabbit allergen

“…The peptide components are from 2 subfamilies: lipophilins A/B and lipophilin C. They belong to the secretoglobin branches 1D and 2A, respectively. Lipophilins have been found to be major constituents of some mammalian secretions, including the tears of rabbits 26 and human subjects and the prostatic fluid of rats. 24 In contrast to the apparently restricted expression of rabbit lipophilins in lacrimal, salivary, and prostate glands, there is evidence that human lipophilins are expressed in a wide variety of tissues, including salivary glands, the thymus, skeletal muscle, and the trachea.…”

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“…This result was unexpected because in-solution digests of protein mixtures, in our experience, can readily identify several hundred proteins in a single analysis [32]. This difference in the number of proteins identified by each method could partly be caused by the high 'dynamic range' of tear fluid, in which 80% to 90% of the protein content is represented by a minor group of proteins [17], which may make the identification of the lower abundant proteins difficult without pre-fractionation of the sample. Although we have no direct evidence, we also speculate that the inefficiency of the in-solution digestion could result from a lack of efficiency of the protocol itself, or from the high number of protease inhibitors and proteases present in the sample.…”

“…We were able to retrieve a total of about 60 described identifications and Harding [15] mentions a tear fluid proteome of about 80 proteins, including proteins only present in special conditions, such as allergy. The relatively low number of proteins identified, compared to other body fluids, may be due to the limited sensitivity of the methods employed [16], as well as the challenging composition of the tear fluid proteome, in which three proteins (lipocalin, lysozyme and lactoferrin) correspond to approximately 80% of the total protein concentration [17]. …”

Human tear proteomics and peptidomics in ophthalmology: Toward the translation of proteomic biomarkers into clinical practice

“…Interestingly, it revealed that the gel-based approaches might be useful in such analyses. This is likely due to the high "dynamic range" of the tear fluid, in which 80 to 90% of the protein content is represented by a small group of proteins including lipocalin, lactoferrin, lysozyme, secretory IgA (sIgA), and serum albumin (34).…”