This article was contributed by Elke Babiuk. (Thanks,
Elke!)
FLUORIDE-MAGNESIUM INTERACTION (Guest Editorial)
by A Machoy-Mokrzynska (Institute of Pharmacology and
Toxicology, Pomeranian Medical Academy, Szczecin, Poland)
Fluoride (J. of the International Society for Fluoride
Research), Vol. 28 No. 4; November, 1995, pp 175-177
It has now been fifteen years since Marier drew attention to
the significance of magnesium in biological interaction with
fluorides.(1) The toxic effect of fluoride ion plays a key role
in acute Mg deficiency. The amount of F- assimilated
by living organisms constantly increases, and Mg absorption
diminishes as a consequence of progressively advancing
industrialization. Marier gives examples of such retention of
both elements in plants (e.g. in pine and tomatoes) and
in animals, for instance in bone tissue, blood and kidneys, with
the last being thought as the most probable place of
Mg-F- interaction.(1) Now, further facts have been
observed, which throw a new light on the effects of
Mg-F- interaction.
The significance and distribution of Mg in living organisms
are widely known and described in textbooks.(2) Fluoride ion
clearly interferes with the biological activity of magnesium
ion.(3) Present-day Mg deficiencies in humans are the result of
intensive expulsion of this element (e.g. under the
influence of extensive drinking of alcoholic beverages) or
reduced Mg content in the diet, caused, for example, by
inappropriate agricultural practices or effects of
ecotoxins.(4)
One of the prime locations of possible F- and Mg
interactions is the intestines. The increased F-supply
reduces intestinal Mg resorption, owing to high chemical affinity
of both elements and production of MgF+ and
MgF2.(1) However, there are many facts to be
considered, since there is a common mechanism of transportation
of both these elements through the intestinal walls. Distinct
F--Mg interaction is also observed in other cells and
tissues. Mg deficiency in plants may limit synthesis of
chlorophyll, on which photosynthesis depends. Therefore,
supplementation of Mg protects plants against toxic effects of
fluoride compounds.(1) Mg deficiency in animals reduces
production of energy, relevant to the Mg-ATP system. Reduction of
ATP levels affects in an unfavourable way many metabolic
processes connected with the action of ATP (eg, metabolism of
carbohydrates, proteins, nucleic acids, lipids, and active
transport).
The role of Mg and F- ions in enzymology is also
well known. Magnesium-dependant enzymes compose the biggest group
in enzyme systematics. Magnesium is the activator of more than
300 enzymes, while fluorine is known as their inhibitor, although
the activity of some enzymes is known to be increased by
fluorine.(5) In general, Mg-F- interactions most
frequently decrease enzymatic activity.(6) The greatest practical
significance of Mg-F- interaction however, seems to be
in processes of bone and tooth mineralization, and in the
formation of uroliths.(7,8)
In bone tissue magnesium stimulates the transformation of
immature (amorphic) bone into a more crystalic form. Owing to the
translocation of Mg into mineral tissue, bone elasticity
increases to help prevent fractures. Rats on diet poor in Mg
display significantly higher content of F- in femurs
and molars. This is undoubtedly related to the assimilability of
both elements. Since bioavailability of Mg and F-
depends on their mutual ratio in the diet,(9) a low-magnesium
diet distinctly increases F- absorption in the
intestines.
Taking into account the mineralization of bone tissue, one
also cannot ignore the role of calcium. The basic inorganic
compound of bones is hydroxyapatite, containing calcium
phosphate. The far-reaching antagonism between magnesium and
calcium affects not only their different distribution in tissues,
but also their mutual dislodging from cells. For example,
magnesium favours blocking of calcium channels, disturbs
oxidative phosphorylation, intensifies bone decalcification and
increases muscle-cell diastole, while calcium intensifies
contraction. On the other hand, hypercalcemia enhances Mg loss or
magnesiuria.(10)
Mg-F- interaction processes relating to enamel and
its effect on caries have also been investigated. Fluoride ion
affects enamel hardening (11, 12) and prevents its annealing, but
this effect diminishes after administration of Mg. Magnesium
alone does not visibly affect tooth plaque, erosive enamel
damage, or the course of caries, but Mg and F-
administered jointly influence enamel hardening and reduce caries
significantly, as demonstrated in rats.(13) In interactions of
F- with Mg and Ca, it should be stressed that it is
calcium rather than magnesium that intensifies mineralization
processes.
Urolith formation is considered to be pathological. Mineral
content analysis of uroliths shows that they always contain Mg
and F- (besides phosphates, calcium and other
inorganic and organic components).(8) Formation of uroliths
follows crystallization rules. Mg ion reduces the rate of
superficial crystal nuclei formation, whereas F- ion
accelerates the process. The former reduces and the latter
accelerates growth of calcium phosphate crystals.(7) In the
formation of uroliths, calcium is the promotor, and magnesium
plays the role of the inhibitor.
It also should be pointed out that uroliths always contain
more Ca than Mg. Fluoride on the other hand, favours formation of
uroliths and accelerates their production.(8)
In summary, it can be stated that in intoxication with
fluorine compounds, magnesium plays a protective role by
countering and reducing the toxic effects of F-.
References:
1 Marier J R. Observations and implications of the (Mg F)
interrelations in bio-systems: a review and comments on magnesium
intake and fluoride intake in the modern-day world. Proceedings
of the Finnish Dental Society 76. 82-92, 93-102, 1980.
(Abstracted in Fluoride 14, 142 1981).
2 Durlach J. Le magnesium en pratique clinique. Editions
Medicales Internationales. Paris 1991.
3 Guminska M. The effect of magnesium on metabolism in living
organisms and medical consequences of its deficiency in man.
Folia Medica Cracoviensia 26 1-2, 5-28, 1985.
4 Markiewicz J. Environmental factors decreasing magnesium
content in alimentary chain. Folia Medica Cracoviensia
26 1-2, 5-28, 1985.
5 Strochkova L S, Zhavoronkov A A. Fluroide as an activator of
enzymatic systems. Fluoride 16, 181-186 1983.
6 Chlubek D, Machoy Z. Significance of the effect of fluorine
dose on enzymes activity in vivo and in vitro studies.
Bromatologia i Chemia Toksykologiczna 22 3-4, 235-242,
1989.
7 Okazaki M. Mg2+-F- interaction during
hydroxyapatite formation. Magnesium 6 (6) 296-301,
1987.
8 Machoy P, Bober J. Fluorine-constant component of urinary
calculi, Environmental Sciences 2 1 11-15, 1993.
9 Cerklewski F L. Influence of dietary magnesium on fluoride
bioavailability in the rat. American Insitute of
Nutrition 117 (3) 456-500, 1987.
10 Machoy Z. Biochemical mechanisms of fluorine compounds
action. Folia Medica Cracoviensia 28 1-2, 61-81,
1987.
11 Collys K, Slop D, Coomans D. Interaction of magnesium and
fluoride in the rehardening and acid resistance of
surface-softened bovine enamel in vitro. Magnesium Trace
Element 9 (1) 47- 53, 1990.
12 Luoma A R, Luoma H, Raisanen J, Hausen H. Effect of
magnesium and fluoride on the fermentative dissolution of enamel
by a streptococcal layer as measured by mircrohardness tester and
a proton probe microanalysis. Caries Research 17
430-438, 1983.
13 Sorvari R, Koskinen-Kainulainen M, Sorvari T, Luoma H.
Effect of a sports drink mixture with and without addition of
fluoride and magnesium on plaque formation, dental caries and
general health of rats. Scandinavian Journal of Dental
Research 94 483-490, 1986.
FLUORIDE: published by the
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