Enamel Fluoride in Nursing Rats with Mothers Drinking Water with High Fluoride Concentrations

Abstract

The purpose of this study was to determine the F levels in plasma and molar enamel from rat pups whose mothers had received various levels of F during pregnancy and/or lactation. Rats were started on water containing 0 (Group I), 50 (Group II), or 100 (Group III) ppm F at the beginning ofpregnancy or on the day of delivery. The mothers and pups were killed 13 days after delivery, and plasma F levels, milk Flevels, and pup molar enamel F levels were determined. (Ericsson, 1969;Ericsson and Ribelius, 1970;. Baseline values of F content in developing rat molar enamel have not been reported, nor has the effect of increasing the maternal F intake on plasma F levels and enamel F uptake in the pups been documented.The purpose of this study was to determine the F levels in plasma and molar enamel from rat pups whose mothers had received various levels of F during the pregnancy and the lactation periods, or the lactation period alone. Mother rats of an additional three litters were given water containing 50 ppm F. One-half of the pups in each litter were removed from the mother while actually nursing, and the other half were taken from the mother one to two hours before plasma was obtained from the pups.The F in each of the plasma samples from mothers (mean volume: 0.99 ml + 0.026) and pups (mean volume: 0.62 ml + 0.10), milk samples (mean volume: 0.80 ml + 0.180), and pooled enamel samples (mean weight: 13.91 mg ± 5.07) was concentrated by the rapid microdiffusion method of Taves (1968) as modified by Whitford and Reynolds (1979). Fluoride analyses were done using an ion-specific electrode. The percent recovery values were established using the known addition method (Taves, 1968). The differences in mean values were statistically evaluated using the Student t test (signifcant if p < 0.05).Because initial milk F concentrations were unexpectedly high, human milk samples were analyzed in the same series with subsequent rat milk samples. To test for possible contamination from fur and skin, de-ionized water was dropped on and collected from two animals and assayed for F. Results.At each of the fluoride intake levels, the data collected from animals exposed to fluoride both pre-natally and post-natally and from animals exposed only post-natally were not significantly different. Thus, the pre-natal-pluspost-natal and post-natal-only data were combined in each of the three F intake groups. Group I contained four mother rats and a mean of 10.0 + 1.4 pups per litter; Group II, five and 7.6 + 3.8; and Group III, six and 8.0 + 1.8.The percent recovery achieved by the analytical method was: 82% for mothers' plasma, 98% for milk, 67% for pups' plasma, and 75% for pups' enamel. The measurement error was + 2%.877

Prenatal Fluoride Exposure: Measurement of Plasma Levels and Enamel Uptake in the Guinea Pig

“…It appears that relatively minor changes in fetal plasma fluoride concentrations led to relatively large increases in fluoride uptake in the fetal enamel. These findings are in agreement with those from a recent study involving enamel fluoride changes in nursing rats in which fluoride levels in developing enamel responded markedly to small increases in the pups' plasma fluoride levels (Drinkard et al, 1985). It is apparent that fluoride uptake in developing enamel is increased to a relatively large extent in response to small absolute changes in fluoride concentration in fetal extracellular fluids.…”

Fluoride and Calcium Content of Enamel Organ, Muscle, Liver and Plasma in Rats

“…However, the same general relation ship between plasma fluoride levels on one hand and liver and muscle levels on the other was observed in adult rats. The mean plasma [F] was slightly lower than we have re ported for adult rats in the past [Drinkard et al, 1985[Drinkard et al, , 1987, Whitford et al [1991] have reported mean baseline plasma [F] values for rats of 0.7 pmol/1 (0.013 ppm). Their rats were on standard rat chow and drinking water con taining 0.9 ppm F. Our rats were on standard chow and wa ter with 20 ppm F. However, our rats did not have access to water for 2 h prior to sacrifice.…”

“…We speculate that these low values occur in suck ling rats because rat milk contains less than 0.1 ppm F [Drinkard et al, 1985]. Consequently, F intake is low.…”

Effect of Systemic Fluoride on Rat Molar Morphology

“…The fluoride levels were chosen based on recom mendations for proper growth and development in rats [National Research Council, 1978], The finding that the group which drank water with 50 ppm F" had significantly smaller pups was both unexpected and is in contrast to the results of Gray [1973] and Drinkard et al [1984] for the same concentration. Although the body size was decreased, the tooth size was not af fected.…”