The effect of low doses of fluoride on tissue enzyme activity in the rat

Arch\ oralBid

Vol. 21, pp. 441 to 448. Pergamon Press 1976.Panted in Great Bntam.

SHORT COMMUNICATIONS THE EFFECT OF LOW DOSES OF FLUORIDE TISSUE ENZYME ACTIVITY IN THE RAT

ON

D. B. FERGUSON Department

of Physiology,

Medical

School,

University

of Manchester,

Manchester

Ml3

9PT, England

serum alkaline phosphatase activity decreased in rats given drinking water containing 10 ppm fluoride over 6 weeks, no significant change in activity was observed in liver or intestinal tissue. Acid phosphatase, glutamic oxalacetic transaminase, glutamic pyruvie transaminase and leucine aminopeptidase activities showed no significant changes in serum, liver, kidney or intestine.

Summary-Although

Previous work (Reikstneice, Myers and Glass, 1965; Ferguson 1971, 1976) has shown small changes in the activity of serum enzymes in the rat, the rabbit and in man after administration of fluoride in the water supply. Speirs (1973) was unable to find any consistent changes in alkaline phosphatase activity in rabbits and human subjects after fluoride administration; in rats, he found that half his animals showed a significant decrease in alkaline phosphatase activity and ascribed it to decreased activity of the liver isoenzyme. As much serum enzyme activity results from enzymes produced by specific tissues, it is possible that small changes in serum may reflect larger changes in the tissues. If fluoride ions, in concentrations comparable to those used in water fluoridation, may cause small changes in serum enzyme activity, estimation of tissue enzyme activities is necessary to discover whether these indicate significant effects on metabolism. Twenty rats, all previously drinking non-fluoridated water and receiving a similar diet, were used in this experiment. The mean fluoride intake was about 30pg/day. Twelve rats were transferred for six weeks to water fluoridated at 10 ppm F-. This increased the fluoride intake by 330 pg/day. All the animals were killed and the liver, kidney and ileum removed, These tissues were homogenised in a Waring blender in iced saline for 20 min and the resultant extracts assayed for activities of glutamic oxalacetic transaminase (EC 2.6.1.1, GOT). glutamic pyruvic transaminase (EC 2.6.1.2., GPT), acid and alkaline phosphatases (EC 3.1.3.2 and 3.1.3.1.) and leucine amino-peptidase (EC 3.4.1.1.) LAP) with Boehringer TEST combination kits (Boehringer Corporation London. Ltd., 54-58 Uxbridge Road, Ealing, London W5 2TZ). The substrate for the phosphatases in these kits is p-nitrophenyl phosphate. A blood sample was also taken and the activities of these enzymes in the serum estimated. Changes of enzyme activity in the rat serum were small. A decrease in alkaline phosphatase activity was statistically significant (p < 0.05) but small increases in transaminase activity and decreases in the other enzyme activities were not. In the tissues, there were 447

no changes reaching statistical significance but there was a trend towards increase in transaminase activity and decrease in LAP activity. Similarly, there were trends towards a slight increase in activity of both phosphatases in the liver, a slight decrease in the kidney and a slight increase in the ileum. The observations on serum activities were similar to previous observations for alkaline phosphatase. Although GOT activity tended to increase in the serum, this was not a statistically significant increase as in the rabbit (Ferguson, 1975). Although the changes in enzyme activities, other than that of alkaline phosphatase, are not significant, it is interesting that they parallel those observed by Doberenz et al. (1964) in rat serum and liver which also did not reach statistical significance. The changes in enzyme activity in the tissues I found appear to be unrelated to the serum changes, both serum alkaline phosphatase and serum GOT activity decreasing while tissue activity rose. This would, however, be a similar effect to that observed by Doberenz er al. who found that isocitric dehydrogenase activity in animals on very low fluoride diets was increased in serum and decreased in the tissue of origin, the liver. The suggestion put forward previously (Ferguson, 1971) that fluoride ions might influence loss of enzymes from cells rather than affecting metabolic pathways would be supported by my present observations. Although statistically some of these changes are significant, their magnitude is small and the results given an impression of chance variation rather than of a clear effect on metabolic function. A much larger experiment involving many more animals, possibly of several species, and covering a wide spectrum of enzymes is needed to investigate whether low doses of fluoride can have adverse metabolic effects.

REFERENCES Dpberenz A. R., Kurnick A. A., Kutz E. B., Kemmerer A. R. and Reid B. L.. 1964. Effects of a minimal fluoride diet on rats. Proc. Sot. rxp. Viol. 117. 68-693. Ferguson D. B., 1971. Effects of low doses of fluoride on serum protein and a serum enzyme in man. Nature NW Bid. 231. 159%160.

448

D. B. Ferguson

I

Ferguson D. B., 1976. The effects of low doses of fluoride on enzyme activity in rabbtt serum. Archs orul Bid. 21. 449450. Reikstneice E., Myers H. M. and Glass L. E., 1965. 1~1 viva effects of sodium fluoride on serum proteins and enzymes as studied with starch gel electrophoresis. Arch orul Biol. 10. 107 -I 17. Speirs R. L.. 1973. Total serum alkaline phosphatase and isoenzyme activities after ingestion of fluoride in man. the rat and rabbit. J. dcnr. Rus. 52. 984.

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