The flow rate and composition of human labial gland saliva

i%RCHIVES

8iAL

PERGAMON

Archives of Oral Biology 44 (1999) S 11-S 14

BIOLOGY

The flow rate and composition of human labial gland saliva David B. Ferguson Schoolof Biological Sciences, University of Manchester, Manchester, M23 IPL, U.K

Since The flow rate of saliva from human labial salivary glands has usually been measured as the secretion from an area of labial mucosa as 0.05 - 4.8 p.l/cm&in. The only data for single glands gives a comparable figure of 0.1 p.l/miu/gland . Then is no consemms on the effects of gustatory stimulation, gender or ageing, although most reports suggest that flow rate is not related to gender and ageing up to age 60. The main differences in composition between labial gland saliva and that from the major glands are the higher and variable sodium concentration, the very low phosphate and hydrogen carbonate concentrations, and the higher protein concentration despite low concentrations of amylase. The concentrations of IgA and blood group substances are notably higher iu labial gland saliva. In Sjogren’s syndrome and cystic fibrosis flow rates are decreased. Low rates of flow have been associated with a higher incidence of dental caries. Key words: labial salivary glan& salivary flow rate, salivary compc&ion,protein,amylase,human The secretions of the minor salivary glands have received much less attention than those of the major glands because of the small size and scattered nature of the glands. However, the total number of minor salivary glands has been estimated at around 600 (Provema, 1964) and their contribution to the toti volume of saliva, estimated by subtracting the measured secretion from the major glands from the total volume expectorated, has been assessed at 612% in both unstimulated and stimulated flows (Dawes and Wood, 1973a). The most accessible minor salivary glands are the labial glands, located on the inner surfaces of the lips. This paper reviews the data currently available on the flow rate and composition of labial gland saliva. Methods of collection of laGa1 gland saliva If saliva is collected for analytical purposes there is no necessity to measure flow rate provided that the actual volume collected can be measured. Kaaber (1977), Green and Embery (1985) and Makinen et al. (1983) used pieces of filter paper or tiher paper discs applied to the labial mucosa, Smith et al. ( 1992) pieces of sponge, and Shiba et al. ( 1980) a specially designed plastic collector. A number of research workers used capillary tubes, drawing up the secretion by capillarity (Crawford et al., 1975, Hensten Pettersen, 1975, Slomiany et al., 1983, Makinen et al., 1983) or by suction @awes and Wood, 1973b). Such *&responding author. Tel: +36-l-210415 Fax: +36-l-210-4421 0003-9969/99/$-see front matter 0 1999 Published Pll: SOOO3-9969(99)00043-6

by Elsevier

methods camrot determine the effect of changing flow rate on composition. Most analyses have been described as relating to unstimulated saliva unless specific gustatory or mechanical stimulation has been used, although contact of the collecting medium with the lip surface or manipulation of the lip may be in themselves mechanical stimuli. More recently methods have been devised to measure the flow rate from areas of lip surface or from individual glands. The saliva collected may or may not have been analysed. If both flow rate and composition are assessed on the same samples, the effect of varying flow rate on composition can be asc&ained Filter paper pieces of kuown size cau be used to estimate flow rate tiom measured areas of mucosa (Wiesmann et al., 1972, Gandara et al., 1985, Gaubenstock , 1995). Gaubenstock stained the filter paper with fuchsin a&r removal and was able to count individual glands and measure their flow rates from the size of each circle of saliva The gravimetric method of measurement may involve loss of fluid by evaporation and underestimate the secretion rate. The advent of the Periotron, a device which rapidly measures by conductivity the amount of fluid absorbed onto a filter paper strip of defined size, provided an easier and more efficient way of measming the flow rate from a fixed area of labial mucosa. This method was used by Shern et al. (1990, 1993), Sivarajasingam and Drummond (1995) and Eliasson et al. (1996). Saliva collected on filter paper Science

Ltd. All rights reserved.

D. B. Ferguson /Archives

s12 Table 1.

of Oral Biology 44 (1999) ~11-.714 Table 2. Inorganic ions (mmolil) in labial gland saliva

Flow rates of labial gland saliva @km%in

componmt

Wiesmannetal.

Dawes&

Wiesmann et al. 1972

meen5s.d.

2.95k1.25

Sodium

4-15

3-38

30-125

Spiers, 1984

range

0.5 - 1.5

Potassium

1230

lo-30

4-20

Gandara et al. 1985

meanks.d.

4.049.72

Chloride

16-54

Shorn et al., 1990

mean

0.78

Calcium

1.6-3.2

Shorn et al., 1993

mean

0.96

-ionic

2.3811.05

Phosphate

Sivarajasingam & Dmmmond, 1995 mean&xd.

Wood

Ferguson

2.4-5.8 0.3-1.75

0.25-1.07 0.5-0.6

0.29-1.22

0.4-1.2

mean2s.d.

0.063&0.03

Magnesium

Ferguson, 1996

mear&s.d

O&&O.31

Eliasson et al., 1996

mean&s.d

4.759.3

sodium and chloride concentrations were higher when the glands were stimulated by sour lemon drops, whilst phosphate concentrations were lower. I found concentrations of the main physiological inorganic components in saliva collected l?om single glands to be similar to those reported by Dawes and Wood in saliva pooled from many glands (Perguson and Allonby, 1990, Ferguson, 1991, 1994). Saliva from glands with higher flow rates contained higher concentrations of sodium and chloride and lower concentrations of phosphate. The most marked differences from vale in parotid saliva were the lower phosphate concentrations and the apparent absence of hydrogen carbonate. Calculations of anioncation balance showed that chloride ions almost balanced the sum of sodium and potassium ions. The liuear relationship between sodium concentrations and flow rate observed in parotid saliva (Ferguson, 1989) is not observed in labial gland saliva: the variability of the sodium concentrations may be explained by the known variation in length of the striated ducts in minor glands (Hand et al., this issue). Measurements with miniature calcium electrodes suggest that the proportion of calcium in the ionised form is only about 35% (Perguson, 1994). This is a smaller proportion than that in parotid saliva and may be due to the higher protein concentration available for binding calcium. Boros et al. (this issue) report on the fluoride content of labial gland saliva.

Gaubensto&

1995

1

Individual glands (@hnin&nd) Ferguson, 1996

range

Gaubenstock, 1995 (slow flow group) mean+s.d

0.005-0.24 O.lSfl.09

strips cannot be used for chemical analysis because of the smallness of the sample iu relation to contaminating substances from the strip itself A non-contact method of measurement is provided by photographic recording and this permits subsequent collection by glass capillary tubes of saliva secreted at known flow rates (Ferguson, 1996). This method allows measurement of secretion from individual glands and from defmed areas of mucosa. Spiers (1984) designed a plastic suction device to collect from a known area. Some disadvantages of filter paper absorption methods (notably possible evaporation and the need to keep the mouth open) are overcome in a new appliance described in this symposium (Doros et al., this issue). Flow rate of labial gland saliva The mean flow rate ofunstimulated labial gland saliva as measured by the above methods varies up to 5 cl/cmVmin although most observers estimate it as below 1 Irycm2/min (Table 1). The flow rate from individual glands is between zero and 2.24 @mitt (Ferguson, 1996). The effect of stimulation on flow rate is still debatable: Speirs ( 1984) reported incmases t?om an unstimulated rate of 1.1 @/mm up to 3.96 @/mitt with ascorbic acid stimulation, 2.62 @/mm with salt stimulation and 4.36 ul/min with chewing. However this last figure is very high because of the values from one subject and if he is excluded the mean comes down to 2.1 pEnin. Shem et. al. (1993) were unable to demonstrate any difference between stimulated and unstimulated flow rates. Sivarajasingam and Drummond (1995) found small increases in flowrate from labial glands but not corn minor glands in other sites in response to. Other reports suggest no difference with stimulation. Composition of labial gland saliva -Inorganic (Table 2) The inorganic components of labial gland saliva were fust reported by Dawes and Wood (1973b). They reported that

Composition of labial gland saliva - Organic components (Table 3) The original analyses of Dawes and Wood (1973b) included two organic components - urea and total protein The values later obtained by Ferguson (1991) for total protein in individual gland secretions by a di&rent method are similar. Analysis of individual proteins has been less detailed and often purely qualitative, with the exception of the immunogloblins which have been studied more extensively because of their possible role in oral protection. Crawford et al. (1975) demonstrated concentrations of IgA in labial gland saliva to be substantially higher than those in major gland salivas, aud this work was extended by (1975) and Smith et al. iu 1991. He&en-Pet&son Makinen et al. (1983) assayed a number of enzymes in

D. B. Ferguson /Archives Table 3. Organic c.omponents of

Total protein (g/1)1.45-5.00

of Oral Biology 44 (1999) SII-S14

labial gland saliva

s13

Ferguson (1996).

@awes & Wood, 1973b)

Variation in labial gland saliva in disease states

0.40-5.35

(Ferguson,1991, 1995)

AlilylilSe

1.0-12.0m&l

(HenstenPettersen, 1975)

Lysozyme

3.0-4.0 m&l

(Hen&n Pettersea,1975)

There are no reports on the flow rate of minor gland saliva in patients complaining of xerostomia although my personal observations of pateints with radiation-iuduced xerostomia indicated that the number of active labial glands and their rates of secretion were substantially reduced - sometimes to zero.

Blood

group substances- A, B, L@,Leb

Virus haemagglutinaticmfactor IgA

194 rngn

(Crawford et al., 1975)

Isc

5 mg/l

(Crawford et al., 1975)

IgM


(Crawford et al., 1975)

Anti-HIV, Complement Mucin, peroxidase, urea.

proteins CD55, CD59 and SP40,40

lactoferriq

fibronectin, kalhkreii

magainiq

labial gland saliva and found very low concentrations of amylase, lysozyme, aryl amidases and kallikreiu. There is histological evidence to suggest that peroxidase may be present in labial &id saliva (Reitamo et al. (1977). Lingual lipase and von Ebner’s gland protein found in the secretion of von Ebneis glands (Blaker et al., 1993), are not present in labial gland saliva. Fibronectiu has beeen assayed, and two antibacterial proteins, lactoferrin and magainin (Wolff et al., 1990) are found in labial gland saliva. Mucins are more difficult to quantitate but the concentration of blood group substances has been measured and found to be much higher than in saliva from the major glands. Physiological variation in labial gland saliva flow rate and composition Reference has aheady been made to variations in flow rate resulting f?om di&rent stimuli. The parasympathomimetic drug pilocarpine has been used to increase flowrate (Rhodus, 1997). A range of opinion sexists over the question of age effects on labial gland flow rates. Gandara et al. (1975) and Smith et al. (1992) found a significant decrease in flow rate with age, whilst Shern et al. (1993), observed negligable changes. Ferguson (1996), and Eliasson et al. !996) were unable to detect any correlation between age and flow rates. Sivarajasingam and Drummond (1995) stated that flow rate decreased with age but close examination of their data shows that the decrease occurred only after age 60. Variation of labial gland salivary flow rate between sexes was reported by Sivarajasingam et al. (1995) and Eliasson et al. (1996) with w’omen having lower flow rates, but no difference between the sexes was observed by Gandsra et al. (1985), Smith et al. (1992), Shern et al. (1993) or

Diseases affecting the salivary glands have the expected effects upon labial glands. Thus Rhodus (1997) showed that in both primary and secondary Sjogren’s disease the mean resting flow rate were low but the glands could be stimulated by pilocarpine. Wiesman et al. (1972) showed that in cystic fibrosis the mean flow rate was reduced by over 40% and sodium concentrations were increased t?om 4-15 mmol/l to 8-40 mmol/l. Gandara et al. (1985) found a decrease in sour lemon drop stimulated labial gland saliva flow rates from 2.07fl.23 to 1.56 + 0.23 clymin in patients sutfering from oral lichen planus, but this difference was not significant. The labial glands secrete saliva in close proximity to the tooth surfaces and it might be expected that their secretion rates might inthtence the initiation or progress of dental caries. Speirs (1984) observed that the unstimulated flow rate of labial gland saliva was 1.04 + 0.63 pl/rn.in/cm~ in subjects with caries f&e anterior teeth but only 0.53 5 0.19 pl/rnin/cm2 in subjects with carious anterior teeth. Stimulation of flow gave similar figures: 3.21 +_2.00 and 2.30 + 1.50 pl/min/cm2 respectively. Gaubenstock (1996) found caries tiee subjects to have more glands/unit area of mucosa and higher flow rates than caries susceptible subjects. Conclusions It is clear that while much work has been carried out on labial gland saliva secretion rates and composition, there still remain large gaps in our knowledge and discrepancies between observations. This paper has summa&d the present extent of our knowledge and provides baselines for further observations.

References Blaker, M., Koch, K., Ahlers, C., Buck, F., S&male, H. 1993. Molecular cloning of human van Ebner’s gland protein, a member of the lipocalin superfamily highly expmased in lingual salivary glands. Biochim. Biophys. Acta 1172, 131-137. Crawford, J.M., Taubman, MA, Smith D.J., 1975. Minor salivary glands as a major source of secretory immunoglobulin A in the human oral cavity. Science 190, 1206-1209. Dawes, C. Wood, C.M., 1973a. The contribntion of the oral minor mucous gland secretions to the volume of whole saliva in man. Archs oral biol. 18, 337-342.

514

D. B. Ferguson /Archives

Dawes, C, Wood, C.M., 1973b. The composition of human lip mucous gland secretions. Arcbs. Oral Biology. 18, 343-350. Eliasaon, L., Birkhed, D., Heyden, G., Stromberg N., !996. Stud& on human minor salivary gland secretions using the Periotron method. Archs. oral Biol. 41, 1179-l 182. Ferguson, D.B., 1989. Salivary electrolytes. in Tenovuo, J.O. (ed) Human Saliva: Cliical Chemistry and Microbiology. Vol. I. CRC Press Inc., Boca Raton, USA Fequaon, D.B., Allonby, L., 1990. Sodium and potassium corm&muons in labial gland saliva J. Dent Res. 69,983. Ferguson, D.B., 1991. Protein and phosphate concentrations in the secretions of individual labial salivary gland?.. J. Dent Res. 70,670. Ferguson, D.B., 1994. Total and ion&d calcium in individual labial glaud saliva J. Dent Rea. 73,423. Ferguson, D.B., 1995. Proteim of labial gland saliva J. Dent Rea. 74,844. Fergusoq D.B., 1996. The flow rate of mtstimulated human labial gland saliva J. Dent. Res. 75,980-985. G&am, B.K., Izutsu, LT., Truelove, E.L., Man&l, I.D., Sommers, E.E., Ensign, W.Y., 1985. Sialochemistry of whole, parotid aud labial minor gland saliva in patients with oral lichen planus. J. Dent Rea. 66, 1619.1622. Gaubenstoc~ L.M., 1995. Dental caries and the secretory activity of human labial minor salivary glands. Archs. oral biol. 40,525-528. Green, D.RJ., Embery, G., 1985. The chemistry and biological pmpertiea of minor salivsry gland secretions. In: Oral interfacial reactions of bone, sofl tissue and saliva Ed Glantz, p.O., Leach, S.A, Ericson, T. IRL Press, Oxford. He&en-Pet&son, A, 1975. Biological activities in human labial and palatine secretions. Archs oral Biol. 20, 107-l 10. Kaaber, S., 1977. Sodium and potassium content in human palatine gland secretion Archs Gral Biol. 22, 529-532 Makinen, KK, Viien, K.K, Soderlii E., Kotimnta, J., 1983. Compceition of human palatine gland secretions and evidence for specific arylamidaaes. Arcbs. &al biol. 28, 893-894. Prowma, D.V. 1964. Oral histology. Lippincott, Philadelphia Reiio, S., Klockars, M., Rae&, A-M., 1977. hnmunohistochemical identitlcation of lysozyme in the minor salivary glands of man. Archs. Oral Biol. 22, 515-5 19.

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