Anion Translocation Through the Enamel Organ

Abstract

The objective of this study was to determine whether cells of the secretory- and maturation-stage enamel organ of rats contain anion translocation mechanisms similar to those found in other ion-regulating epithelia. Sodium bromide (Br) was used to localize the distribution of anions in the enamel organ. Furosemide, an inhibitor of the Na-K-2C1 co-transporter and other anion transporters, was administered with NaBr or sodium fluoride (F) to investigate if halogens other than Cl can use these transport mechanisms. We obtained the data by using freeze-fracture and freeze-drying methodology in conjunction with scanning and transmission electron microscopy (SEM, TEM) and energy-dispersive x-ray spectroscopy (EDS).

The secretory- and maturation-stage enamel organ prevented Br from entering the enamel matrix. Br was localized in the Tomes' processes, but not in the enamel matrix, strongly suggesting that the distal intercellular junctions of ameloblasts are "tight". Furosemide disrupted anion transport to allow not only Cl but also Br to enter the forming enamel matrix.

Periodic administration of high F doses promoted the formation of bands of disrupted enamel, reflecting the periodicity of F administration. The same concentration of F administered with furosemide increased the severity of disrupted enamel, resulting in "blisters" and pits in the maturing enamel. The enamel "blisters" contained pools of small, disorganized enamel crystallites. The group receiving furosemide only displayed normal enamel structure but had increased C1 in the enamel matrix. This study provides evidence that anion transporters, possibly the Na-K-2CI co-transporter, function to regulate anion translocation, including F, to the enamel matrix in secretory- and maturation-stage enamel organ. These mechanisms may explain why the ionic composition on the cellular side of the anion barrier is different from that of the enamel matrix.

Keywords

Amelogenesis ion transactions fluoride enamel

Get full access to this article

View all access options for this article.

References

Anderson M. , Gregory R. , Thompson S. , Souza D. , Paul S. , Mulligan R. , et al. (1991). Demonstration that CFTR is a chloride channel by alteration of its anion selectivity. Science 253:202-204.

Bawden J. and Crenshaw M. (1984). Effect of inihibition of net calcium uptake on net fluoride uptake in developing rat molars. J Dent Res 63:642-645.

Bawden J. , Deaton T. , Crenshaw M. (1987a). The short-term uptake and retention of fluoride in developing enamel and bone. J Dent Res 66:1587-1590.

Bawden J. , Deaton T. , Crenshaw M. (1987b). Diffusion of fluoride through the rat enamel organ in vitro. J Dent Res 66:1360-1363.

Bawden J. , Crenshaw M. , Wright J. , LeGeros R. (1995). Consideration of possible biologic mechanisms of fluorosis. J Dent Res 74:1349-1352.

Hanrahan J. , Alles W. , Lewis S. (1985). Single anion-selective channels in basolateral membrane of a mammalian tight epithelium. Proc Natl Acad Sci 82:7791-7796.

Martinez J. , Barker S. (1989). Inhibition of 36C1 uptake by stilbene sulphonic acid derivatives and loop diuretics in rat submandibular salivary acini. Arch Oral Biol 34:535-540.

Nakatsuka T. , Fujikake N. , Hasebe M. Ikeda H. (1993). Effect of sodium bicarbonate and ammonium chloride on the incidence of furosemide-induced skeletal anomaly, wavy rib, in rats . Teratology 48:139-147.

Prostak K. , Seifert P. , Skobe Z. (1992). Fish tooth formation: An assessment of biological factors affecting the fluoride content of enameloid. In: Hard tissue mineralization and demineralization. Suga S , editor. Tokyo, Japan: Springer-Verlag , pp. 33-52.

10.

Prostak K. , Seifert P. , Skobe Z. (1993). Enameloid formation in two tetraodontiform fish species with high and low fluoride contents in enameloid. Arch Oral Biol 38:1031-1044.

11.

Skobe Z. , Heeley J. , Kashket S. , Dobeck J. , LaFrazia F. , Prostak K. (1984). Banding of rat incisor enamel following pulsed ingestion of fluoride. In: Tooth enamel IV. Feamhead R , Suga S , editors. Amsterdam: Elsevier Science Publishers , pp. 276-280.

12.

Takano Y. , Crenshaw M. (1980). The penetration of intravascularly perfused lanthanum into the ameloblast layer of developing rat molar teeth. Arch Oral Biol 25:505-511.

13.

Whitford G. (1989). The metabolism and toxicity of fluoride. Meyers E , editor. New York: Karger.

14.

Whitford G. , Reynolds K. (1979). Plasma and developing enamel fluoride concentrations during chronic acid-base disturbances. J Dent Res 58:2058-2065.

15.

Wroblewski J. , Sagstrom S. , Mulders H. and Roomans G. (1989). Strontium and bromide as tracers in X-ray microanalysis of biological tissue. Scanning Microscopy 3:861-864.

16.

Zs-Nagy I. (1989). A review on the use of bulk specimen x-ray microanalysis in cancer research. Scanning Microsc 3:473-482.