Trace elements in human parotid saliva

Although various proteins and some electrolytes have been measured in human saliva, little systematic data about the major and minor elemental components of this body fluid have been obtained. In order to obtain such data, concentrations of C, Na, P, Cl, K, Ca, Sc, Cr, Fe, Co, Zn, Se, Br, Rb, Sb, I, and Cs in human parotid saliva were measured by instrumental nuclear methods. The data obtained confirmed the relative lack of Zn in saliva of patients with hypogeusia (decreased taste acuity) and suggested that concentrations of Na, Cl, Br, and Ca followed the order: normals > hypogeusia > hyposmia (decreased smell acuity). To compare concentrations of elements in saliva with those in blood and urine, absolute concentrations were normalized to that of Na through the use of a concept called an enrichment factor. On this basis, parotid saliva is relatively depleted in Se, Zn, and Fe and enriched for most other elements relative to blood plasma indicating that the fluid is not simply a transudate of blood plasma. Using this same technique, saliva composition was found more similar to urine than blood plasma, being relatively depleted in Se, Cs, and Co, being enriched in I, Br, and Cr and having about the same relative concentrations of P, Cl, Zn, Fe, Ca, K, and Rb. As the total body concentrations of many of the enriched elements in saliva are extremely small, their enrichment in saliva suggests special roles for these elements in the oral cavity. Because of its accessibility, ease of collection, and interaction with some body constituents, saliva represents a useful, albeit neglected, tool in the diagnosis of some physiological and pathological changes in body function and in understanding important aspects of trace metal metabolism.     

Studies on histidine-rich polypeptides from human parotid saliva.

The isolation of an histidine-rich polypeptide from human parotid saliva is described. This polypeptide, termed HRP-1, contains 17% histidine. HRP-1 is a neutral molecule and is a precursor of the cationic histidine-rich polypeptides found in saliva. Results of in vitro saliva incubations suggest that breakdown of HRP-1 is enzyme mediated. Degraded species are smaller in size, more cationic in charge, and higher in histidine content. It is concluded that the many histidine-rich polypeptides in saliva are not all individual gene products and are related by a proteolytic degradation.     

Presence of immunoreactive endothelin in human saliva and rat parotid gland.

The presence of immunoreactive endothelin (IR-ET) in human saliva and rat parotid gland was investigated by radioimmunoassay. The IR-ET concentration (mean +/- SEM) in saliva taken from normal volunteers was 2.0 +/- 0.2 pmol/l (n = 15). The IR-ET concentration in rat parotid gland was 19.2 +/- 2.2 fmol/g wet weight (n = 10). Fast protein liquid chromatography (FPLC) of human saliva extract revealed 6 peaks; one peak eluting in the void volume, one in a position between ET-1 and -3, and the other four in the positions of synthetic ET-1, -2, -3 and big ET(1-38), respectively. A similar pattern of rat parotid gland extract was noted with FPLC, except that there was no peak after the void volume. Presence of endothelin, a potent growth factor, in saliva and salivary gland points to a role in maintaining the integrity of the oral and gastrointestinal tract mucosa.     

Glycosylated proline-rich peptide of human parotid saliva. Circular dichroism study.

The direct monitoring of sugars such as lactose, maltose, saccharose is not only useful at the applied point of view but also at the fundamental point of view for studying enzymology, especially in microbiology and fermentation. Benzyme systems were extensively used in solution for analytical applications in industry and medicine. The progress in the field of immobilization of bienzyme systems [1-3], especially within membranes [4-5], makes possible the production of new analytical devices. From the studies dealing with concentration profiles in artificial enzyme membranes [14], evidence was obtained for a well defined relationship between the local concentration of a metabolite and concentration of the first substrate in the bulk solution. In the described systems a substrate is transformed into glucose within a membrane, the glucose is then transformed in gluconic acid with a local oxygen consumption. The local pO2 level is linked to the glucose oxidase velocity, which is only linked to the glucose production, that is to say to the concentration of the first substrate. The enzyme electrode is based on the transformation of kinetic phenomena (reaction rates) into absolute values (local concentrations) through the diffusion-reaction coupling process. The manufacture of magnetic enzyme electrodes [6] allows convenient use of the active sensors. The pO2 electrode has some adventages, namely the specificity based on the selectivity of the gas permeable membrane and the linear relationship between the oxygen and the output of the electrode. pCO2, pH, ion electrodes give a logarithmic response as a function of the concentration. The grafting of a multienzyme system on a sensor allows a study of sequential systems in a defined context with a measurement of the local concentration of the metabolites. The tool is useful for both kinetics [4] and regulation studies [5].     

Variability of zinc concentrations in human stimulated parotid saliva

The objective of this study was to determine the effect of sample collection conditions on the zinc concentrations in stimulated parotid (SP) saliva. The variability of zinc levels in SP saliva was determined on the basis of different times within a single day, from day-to-day, from one month to the next month, and between subjects. Ten healthy subjects, half of each sex, consumed 15–22 mg Zn/day in their diet. No significant difference in the mean zinc concentration of SP saliva on a day-to-day or month-to-month basis was demonstrated. Three subjects had significantly different SP saliva zinc levels than the other seven subjects. A significant diurnal variation in the mean SP salivary zinc levels was found. Changes of SP saliva flow rates suggested a training effect.     

Chemical and physical characteristics of a phosphoprotein from human parotid saliva.

The isolation of a highly purified phosphoprotein, previously named protein A, from human parotid saliva is described. This protein has an unusually high amount of glycine, proline and dicarboxylic amino acids. Together these amino acids account for 80% of all residues. The protein contains 1.9mol of P/mol of protein, probably as phosphate in an ester linkage to serine, and about 0.5% carbohydrate, but no hexosamine. The N-terminal is blocked and the following C-terminal sequence is proposed: -Aal-Asp-Ser-Gln-Gly-Arg-Arg. The sioelectric point is 4.43. The molecular weight of the protein determined by ultracentrifugation is 9900 and from chemical analyses 11000. Circular-dichrosim and nuclea-magnetic-resonance spectra indicate the absence of polyproline and triple-helical-collagen-like structure for the protein. There is little restriction on the orientation of the single phenylalanine residue in the protein., but there is also an indication of conformational restraint in the protein.     

Purification and characterization of a glycosylated proline-rich protein from human parotid saliva.

1. A glycosylated proline-rich protein (GPRP) was purified to homogeneity by subjecting parotid saliva to immunoaffinity, cation exchange, affinity and hydrophobic chromatography. 2. The purified GPRP had a molecular weight of 78 kDa as analyzed by SDS-PAGE. 3. The amino acid analysis revealed a preponderance of proline, glycine and glutamic acid/glutamine, which accounted for 77% of the total amino acids. 4. Cysteine, tyrosine or phenylalanine residues were not detected. 5. The glycoprotein contained 34% neutral sugars and the oligosaccharides were rich in mannose and N-acetylglucosamine, indicating that N-linked oligosaccharides were the predominant type of oligosaccharides in the molecule. 6. These observations were confirmed by treatment of the purified glycoprotein with specific N-glycosidase which removed the N-linked oligosaccharides leaving a core protein with an apparent molecular weight of 51 kDa. 7. The isoelectric point of GPRP was approx 7.0 and the molecule was not affected by reduction with 2-mercaptoethanol, indicating that no disulfide linkages were present. 8. The GPRP bound to hydroxyapatite and this binding could be partially inhibited by preincubation of the hydroxyapatite with parotid or submandibular saliva. 9. The purified GPRP also bound to a protein with an apparent molecular weight of 95 kDa present in submandibular saliva.     

Isolation and characterization of histamine-releasing peptides from human parotid saliva

Peptides responsible for releasing histamine were purified from human parotid saliva. The amino acid composition of the peptides showed a high proportion of histidine, lysine and arginine. Molecular weights of these peptides were between 3000 and 5000 as determined by SDS-acrylamide gel electrophoresis. These peptides induced histamine release from rat-isolated mast cells accompanied with degranulation in a dose-dependent manner over the concentration range 5-50 micrograms/ml.     

High-performance liquid chromatographic assay for minocycline in human plasma and parotid saliva

A sensitive and specific high-performance liquid chromatographic (HPLC) method with UV detection was developed for the determination of minocycline in human plasma and parotid saliva samples. Samples were extracted using an Oasis™ HLB cartridge and were injected into a C₈ Nucleosil column. The HPLC eluent contained acetonitrile–methanol–distilled water–0.1% trifluoroacetic acid (25:2:72.9:0.1, v/v). Demeclocycline was used as internal standard. The assay showed linearity in the tested range of 0.1–25 μg/ml. The limit of quantitation was 100 ng/ml. Recovery from plasma or parotid saliva averaged 95%. Precision expressed as %CV was in the range 0.2–17% (limit of quantitation). Accuracy ranged from 93 to 111%. In the two matrices studied at 20 and 4°C, rapid degradation of the drug occurred. Frozen at −30°C, this drug was stable for at least 2 months, the percent recovery averaged 90%. The method’s ability to quantify minocycline with precision, accuracy and sensitivity makes it useful in pharmacokinetic studies.     

Purification and partial characterization of four proteins from human parotid saliva

Four proteins, which have been designated A, B, C and D, have been purified from human parotid saliva. These proteins are the major constituents of parotid saliva which migrate rapidly to the anode in polyacrylamide electrophoresis at pH9.5. Gel filtration and polyacrylamide electrophoresis were employed in the purification procedures. After purification all four preparations were tested for homogeneity by electrophoresis at pH2.8 and 9.5, by isoelectric focusing in the pH range 3-10, by immunodiffusion, and by sedimentation in the analytical ultracentrifuge. None of the proteins showed significant activity in assays for amylase, acid and alkaline phosphatase, protease, lysozyme, ribonuclease, peroxidase, beta-glucuronidase, beta-galactosidase, iron-binding activity and esterase. No cross-reactions were detected with antisera specific for lactoferrin and 15 serum proteins. All four proteins were rich in glutamic acid, proline and glycine and were lacking completely the sulphur-containing amino acids. Proteins A and C contained no threonine or tyrosine. Carbohydrate could be demonstrated only in protein A at a concentration of 4% of the total protein.     

Partial purification and characterization of a polymorphic protein (Pa) in human parotid saliva.

A polymorphic acidic protein (Pa) has been isolated from human parotid saliva by the use of ion-exchange and gel filtration chromatography. Following these purification procedures, analytical anionic polyacrylamide disc gel electrophoresis revealed a single stainable band. Amino acid analysis demonstrated a protein particularly rich in proline, glutamic acid, and glycine, but with reduced amounts of threonine and no tyrosine. Only a very small percentage of carbohydrate was detected. Isoelectric focusing at pH 3-10 verified the acidic character of this protein with an isoelectric point in the range pH 3.9-4.5. Other salivary proteins called Pa-II, possibly related physiologically and genetically to the Pr system, were also partially purified and studied. Differences were noted between Pa and Pa-II proteins in molecular size and amino acid composition.     

Conformational study of the basic proline-rich polypeptides from human parotid saliva

The conformational study of two basic proline-rich polypeptides from human parotid saliva, P--D and P--E of known primary structures, was performed by CD and 1H--n.m.r. spectra measurements. These polypeptides contain consecutive sequences of five prolyl residues in their amino acid sequences. The troughs in CD spectra of P--D and P--E were found at 202 and 201 nm, respectively. These wavelengths were different from the value of 206 nm of poly-L-proline form II conformation. In spite of this, the existence of poly-L-proline form II conformation was suggested in the structure of P--D, because the trough for a fragmental peptide of P--D containing five consecutive prolyl residues was found at 204 nm. No remarkable change was detected in CD and 1H--n.m.r. spectra of P--D and P--E in the range of pH 3.0-11.0. The result suggests that no folding of polypeptide which might be affected by ionic interaction exists in its structure.     

Proteome analysis of glandular parotid and submandibular-sublingual saliva in comparison to whole human saliva by two-dimensional gel electrophoresis

The secretions of the salivary parotid and submandibular-sublingual (SMSL) glands constitute the main part of whole human saliva (WS) in which proline-rich proteins (PRPs) and mucins represent dominant groups. Although proteome analysis had been performed on WS, no identification of PRPs or mucins by 2-DE and MS was achieved in WS and no comprehensive analysis of both glandular secretions is available so far. The aim of this study was to compare the protein map of WS to parotid and SMSL secretions for the display of PRPs and mucins. WS and glandular secretions were subjected to 2-DE and spots were analyzed by MALDI-MS. New components identified in WS were cyclophilin-B and prolyl-4-hydroxylase. Also acidic and basic PRPs as well as the proline-rich glycoprotein (PRG) could now be mapped in WS. Acidic PRPs were found equally in parotid and SMSL secretions, whereas basic PRPs and PRG were found primarily in parotid secretion. Salivary mucin MUC7 was identified in SMSL secretion. Thus, the more abundant proteins of WS can be explained mainly by mixed contributions of parotid and SMSL secretions with only few components remaining that may be derived from local sources in the oral cavity.