Animal Proteomics www.proteomics-journal.com
The Saliva Proteome of Dogs: Variations Within and
Between Breeds and Between Species
Sabah Pasha, Taichi Inui, Iain Chapple, Stephen Harris, Lucy Holcombe,
and Melissa M. Grant*
Saliva is a complex multifunctional ﬂuid that bathes the oral cavity to assist in
soft and hard tissue maintenance, lubrication, buﬀering, defense against
microbes, and initiating digestion of foods. It has been extensively
characterized in humans but its protein composition in dogs remains poorly
characterized, yet saliva composition could explain (patho) physiological
diﬀerences between individuals, breeds and with humans. This pilot discovery
study aimed to characterize canine saliva from two breeds, Labrador retrievers
and Beagles, and to compare this with human saliva using quantitative mass
spectrometry. The analysis demonstrated considerable inter-individual
variation and diﬀerence between breeds; however these were small in
comparison to the diﬀerences between species. Functional mapping
suggested roles of detected proteins similar to those found in human saliva
with the exception of the initiation of digestion as salivary amylase was
lacking or at very low abundance in canine saliva samples. Many potential
anti-microbial proteins were detected agreeing with the notion that the oral
cavity is under continuous microbial challenge.
Saliva is a complex multifunctional ﬂuid released into the oral
cavity from a variety of major and minor exocrine glands. Gingi-
val crevicular ﬂuid also ﬂows into saliva contributing tissue and
serum ﬂuids to overall saliva composition. The major functions
of human saliva have been described as: lubrication and phys-
ical protection, buﬀering; clearance of debris, maintenance of
tooth integrity, antimicrobial activity, taste, and digestion.
proteinaceous components of saliva therefore have overlapping
and multifunctional roles to fulﬁll these diverse functions. Given
the breadth of physiological functions of saliva, it is likely that
Dr. S. Pasha, Prof. I. Chapple, Dr. M. M. Grant
Periodontal Research Group
School of Dentistry
Institute of Clinical Sciences
College of Medical and Dental Sciences
University of Birmingham and Birmingham Community Healthcare
Edgbaston, Birmingham, UK
The WALTHAM Centre for Pet Nutrition
Melton Mowbray, Leicestershire, UK
diﬀerences in composition between dog
breeds and between dogs and humans
may help explain physiological and
patho-physiological diﬀerences between
Early explorations of enzyme activities of
dog saliva revealed a lack of salivary amy-
lase in comparison to other mammals,
that it contained high levels of non-
speciﬁc esterase, acid phosphatase, and
munoglobulin A was also reported to be
the most abundant immunoglobulin.
The techniques employed in these early
papers were targeted approaches as the
available technology at the time did not
permit a global approach to assessing
multiple components of canine saliva.
Glycosylated proteins have also been re-
ported to be common in canine saliva.
Salivary glycoproteins have several roles
including tissue lubrication and the
aggregation of bacteria. The lubricating
proteins comprise predominantly mucins, which are highly gly-
cosylated and of high molecular mass in humans. Statherins, ag-
glutinins, histidine-rich proteins, and proline-rich proteins are
also known to aggregate bacteria in human saliva, facilitating
their removal via deglutition and/or immune clearance.
In veterinary medicine, dog saliva has mostly been stud-
ied for cortisol determination,
which varies with breed size,
(where large dogs have lower salivary cortisol), between intact and
and with circadian rhythm.
However, more recently, dog saliva has been used to measure
for non-invasive monitor-
ing of systemic inﬂammation.
Comparisons with human saliva have highlighted that canine
saliva has a higher pH (8.5 vs 6.5–7.5 in humans), buﬀering
capacity, and mineral concentrations.
These diﬀerences may
contribute to dogs being less susceptible to dental caries but more
susceptible to gingivitis due to higher calculus formation.
deed, we have recently followed 52 dogs without an oral hygiene
over 60 weeks and 67% developed periodontitis at 12
or more teeth. Other groups have shown prevalence estimates for
periodontal disease in dogs ranging between 44 and 100%.
In depth analysis of the protein composition of canine saliva
from three mixed breed individuals has been initiated by de
Sousa-Pereira et al. (2015).
Using qualitative gel electrophore-
sis to compare to other mammals, including humans, they
Proteomics 2018, 1700293
2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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