SALIVA

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SALIVA

• Seminar
• Stomatology

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MAJOR FUNCTIONS OF SALIVA

• Solvent
• Buffering
• Lubrication
• Remineralization
• Digestion
• Anti-bacterial
• Anti-fungal
• Temperature regulation
• Production of growth factors and other regulatory
  peptides

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A CONSIDERABLE VOLUME OF SALIVA IS PRODUCED OVER
A DAY

• 0.5 to 1.5 liter of fluid is secreted in a day
• This represents about 1/5 of the total plasma
  volume
• This fluid is not lost as most of it is swallowed
  and reabsorbed by the gut
• Parotis, submandibularis, sublingualis

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THE SECRETORY UNIT
The basic building block of all salivary glands

• Saliva formed in acini flows down DUCTS to empty
  into the oral cavity.

• ACINI - water and ions derived from plasma

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TWO STAGE HYPOTHESIS OF SALIVA FORMATION
Most proteins
Na Cl- resorbed
Hypotonic final saliva into mouth
Water electrolytes
Some proteins electrolytes
K secreted
Isotonic primary saliva
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Inorganic components

• Saliva compositon

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Calcium and phosphate

• Help to prevent dissolution of dental enamel
• Calcium
• 1,4 mmol/l (1,7 mmol/l in stimulated saliva)
• only cca 50 in ionic form
• sublingual gt submandibular gt parotis
• Phosphate
• 6 mmol/l (4 mmol/l in stimulated saliva)
• 90 in ionic form
• pH around 6 - hydroxyapatite is unlikely to
  dissolve
• Increase of pH - precipitation of calcium salts
  gt dental calculus

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Hydrogen carbonate

• Buffer
• Low in unstimulated saliva, increases with flow
  rate
• Pushes pH of stimulated saliva up to 8
• pH 5,6 critical for dissolution of enamel
• Defence against acids produced by cariogenic
  bacteria
• Derived actively from CO2 by carbonic anhydrase

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Other ions

• Fluoride
• Low concentration, similar to plasma
• Thiocyanate
• Antibacterial (oxidated to hypothiocyanite OSCN-
  by active oxygen produced from bacterial
  peroxides by lactoperoxidase)
• Higher conc. gt lower incidence of caries
• Smokers - increased conc.
• Sodium, potassium, chloride
• Lead, cadmium, copper
• May reflect systemic concentrations - diagnostics

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Concentration (mM)
FLOW RATE ml/min
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Organic components

• Saliva composition

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Organic components of saliva

• Mucins
• Proline-rich proteins
• Amylase
• Lipase
• Peroxidase
• Lysozyme
• Lactoferrin
• sIgA
• Histatins
• Statherin
• Blood group substances, sugars, steroid hormones,
  amino acids, ammonia, urea

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Multifunctionality
Amylases, Cystatins, Histatins,
Mucins, Peroxidases
Carbonic anhydrases, Histatins
Anti- Bacterial
Buffering
Amylases, Mucins, Lipase
Cystatins, Mucins
Anti- Viral
Digestion
Salivary Functions
Mineral- ization
Anti- Fungal
Cystatins, Histatins, Proline- rich
proteins, Statherins
Histatins
Lubricat- ion Visco- elasticity
Tissue Coating
Amylases, Cystatins, Mucins, Proline-rich
proteins, Statherins
Mucins, Statherins
adapted from M.J. Levine, 1993
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Mucins

• Lubrication
• Glycoproteins - protein core with many
  oligosaccharide side chains attached by
  O-glycosidic bond
• More than 40 of carbohydrates
• Hydrophillic, entraining water (resists
  dehydration)
• Unique rheological properties (e.g., high
  elasticity, adhesiveness, and low solubility)
• Two major mucins (MG1 and MG2)

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Amylases

• Calcium metalloenzyme
• Hydrolyzes ?(1-4) bonds of starches such as
  amylose and amylopectin
• Several salivary isoenzymes
• Maltose is the major end-product (20 is glucose)
• Parotis 30 of total protein in parotid saliva
• Appears to have digestive function -
  inactivated in stomach, provides disaccharides
  for acid-producing bacteria
• Why is it also present in tears, serum,
  bronchial, and male and female urogenital
  secretions?
• A role in modulating bacterial adherence?

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Lingual Lipase

• Secreted by lingual glands and parotis
• Involved in first phase of fat digestion
• Hydrolyzes medium- to long-chain triglycerides
• Important in digestion of milk fat in new-born
• Unlike other mammalian lipases, it is highly
  hydrophobic and readily enters fat globules

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Statherins

• Calcium phosphate salts of dental enamel are
  soluble under typical conditions of pH and ionic
  strength
• Supersaturation of calcium phosphates maintain
  enamel integrity
• Statherins prevent precipitation or
  crystallization of supersaturated calcium
  phosphate in ductal saliva and oral fluid
• Produced by acinar cells in salivary glands
• Also an effective lubricant

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Proline-rich Proteins (PRPs)

• 40 of AAs is proline
• Inhibitors of calcium phosphate crystal growth
• Part of pellicula dentis
• Subdivided into three groups
• Acidic 45
• Basic 30
• Glycosylated 25

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Lactoferrin

• Iron-binding protein
• Nutritional immunity (iron starvation)
• Some microorganisms (e.g., E. coli) have adapted
  to this mechanism by producing enterochelins.
• bind iron more effectively than lactoferrin
• iron-rich enterochelins are then reabsorbed by
  bacteria
• Lactoferrin, with or without iron, can be
  degraded by some bacterial proteases.

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Lysozyme

• Present in numerous organs and most body fluids
• Also called muramidase
• hydrolysis of ?(1-4) bond between N-acetylmuramic
  acid and N-acetylglucosamine in the peptidoglycan
  layer of bacteria.
• Gram negative bacteria generally more resistant
  than gram positive because of outer LPS layer

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Histatins

• A group of small histidine-rich proteins
• Potent inhibitors of Candida albicans growth

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Cystatins

• Are inhibitors of cysteine-proteases
• Are ubiquitous in many body fluids
• Considered to be protective against unwanted
  proteolysis
• bacterial proteases
• lysed leukocytes
• May play inhibit proteases in periodontal tissues
• Also have an effect on calcium phosphate
  precipitation

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Salivary peroxidase systems

• Sialoperoxidase (SP, salivary peroxidase)
• Produced in acinar cells of parotid glands
• Also present in submandibular saliva
• Readily adsorbed to various surfaces of mouth
• enamel, salivary sediment, bacteria, dental
  plaque
• Myeloperoxidase (MP)
• From leukocytes entering via gingival crevice
• 15-20 of total peroxidase in whole saliva

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CIRCAIDIAN RHYTHM OF SALIVA FLOW

• Time of day

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Effect of feeding on salivary secretion
10 min collection periods
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Variations in salivary composition

• Unstimulated flow
• Submandibular g. 70
• Parotid g. 20
• Accesory g. 7
• Sublingual 2
• Acid stimulation
• Submandibular g. 45
• Parotid g. 45
• Chewing
• Submandibular g. 30
• Parotid g. 60

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Variations in salivary composition

• Parotid secretion increased amylase content
• Submandibular secretion increased calcium
  concentrations

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Gingival cervicular fluid

• Seminar
• Stomatology

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Gingival cervicular fluid

• Synonyms
• Gingival fluid
• Cervicular fluid
• Sulcular fluid
• Similar composition as interstitial fluid
• Flow rate related to degree of gingival
  inflamation, circa 0,5-2,4 ml/day

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Composition

• Cells
• Desquamated epithelial cells
• Neutrophils
• Small amount of lymphocytes and monocytes
• Bacteria
• Inorganic ions
• Similar to plasma
• Potassium 2 x higher than in plasma (cell
  break-up)
• Calcium higher than in oral fluid
• Organic components
• Similar to plasma - serum albumin, globulins,
  complement, protease inhibitors
• Small organic molecules - lactate, urea,
  hydroxyproline
• Enzymes

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Function

• Protective flow towards oral cavity - washes out
  potentially harmful cells and molecules
• Antibacterial - immunoglobulins
• Calcium assists pellicle and plaque fromation but
  may contribute to calculus formation
• Rather response to inflamation