Ionization of Hydrofluoric Acid at 25 °C

Additional beneficial effect of tamarind ingestion over defluoridated water supply to adolescent boys in a fluorotic area

OBJECTIVE

We evaluated the effect of tamarind (Tamarindus indicus) on ingestion and whether it provides additional beneficial effects on mobilization of fluoride from the bone after children are provided defluoridated water.

METHODS

A randomized, diet control study was conducted in 30 subjects from a fluoride endemic area after significantly decreasing urinary fluoride excretion by supplying defluoridated water for 2 wk. Subjects were then assigned to one of two groups, with 15 in each group. One group was supplemented with tamarind (experimental group) for 3 wk and the other (control) group was given only defluoridated water for the same period.

RESULTS

The mean changes in urinary components after tamarind ingestion (volume, pH, fluoride calcium, copper, and magnesium) in the control and experimental groups were compared. There was a significant increase (P < 0.01) in fluoride excretion and urinary pH and a significant decrease in urinary calcium (P < 0.01) and copper (P < 0.05) excretion in the experimental group as compared with the control group. There was no change in urinary volume between groups.

CONCLUSIONS

Tamarind intake appears to have an additional beneficial effect on the mobilization of deposited fluoride from bone, by enhancing urinary excretion of fluoride.

Cimetidine and ranitidine do not affect enflurane metabolism in surgical patients

Hepatic cytochrome-P-450-linked microsomal metabolism is inhibited by cimetidine, and to a lesser extent by ranitidine. Such an inhibition might protect against the metabolite-related toxicity of inhalation anesthetics. However, in comparison with the values measured in a control group, neither cimetidine (600 mg p.o. + 200 mg i.m.) nor ranitidine (150 mg p.o. + 50 mg i.m.), both administered 11-12 h before anesthesia, inhibited enflurane metabolism as assessed by the increase in plasma inorganic fluoride concentration and urinary fluoride excretion in 21 ASA I patients anesthetized with enflurane (end-tidal concentration 0.5 +/- 0.05% for 2-6 h). The inorganic fluoride concentration in the gastric juice remained low in all groups.

Composition of human plaque fluid

The composition of pooled resting plaque fluid was determined in four groups of college-age students (18-22 years), each composed of 50 individuals, who abstained from oral hygiene for 36 hours and did not eat or drink for at least one hour prior to plaque collection. Plaque samples from each group were pooled under mineral oil in small centrifuge tubes and centrifuged at 37,000 g for one hour at 4 degrees C. Supernatants were then combined under mineral oil and centrifuged at 5000 g (4 degrees C) for 15 minutes. In general, the inorganic composition of plaque fluid in the four groups was quite similar and in agreement with values reported by other investigators, but quite different from those of saliva or serum. The mean composition was: Ca, 7.07 +/- 0.51 mmol/L; P, 23.2 +/- 5.3 mmol/L; Na, 18.6 +/- 2 mmol/L; K, 85.1 +/- 5.3 mmol/L; Mg, 3.9 mmol/L; Cl, 42.8 +/- 9 mmol/L; F, approximately 0.004 mmol/L; pH, 5.69 (5.63-6.01). Acetate, propionate, succinate, butyrate, lactate, and formate were determined in two samples analyzed, with acetate and propionate being the predominant acids found. It was also demonstrated, through the titration of one of the plaque fluid samples, that the observed buffer capacity in plaque fluid was mostly related to its organic acid composition. It was noted, however, that when the initial pH in plaque fluid exceeded 6.5, phosphate contributed significantly to the buffer capacity. The contribution of other soluble species (proteins, peptides, amino acids) to the observed buffering in plaque fluid appeared to be small.(ABSTRACT TRUNCATED AT 250 WORDS)

The enamel fluid in the early secretory stage of porcine amelogenesis: chemical composition and saturation with respect to enamel mineral

The present study reports on the separation of fluid from soft, "cheeselike" enamel of porcine permanent teeth in the secretory stage, and the determination of its chemical composition. The enamel tissues were dissected from mandibles of 5 to 6-month-old piglets and pooled under mineral oil in centrifuge tubes, and then centrifuged at 1.9-2.4 X 10(5) g for 1-1.5 hours. The yields of the fluid were 44.8 +/- 2.3 (mean +/- standard error) microliter/g of enamel tissue at 1.9 X 10(5) g, and 53.9 +/- 1.9 microliter/g at 2.4 X 10(5) g. A significant finding was that the total Ca concentration of the enamel fluid (3.9-6.0 X 10(-4) M) was lower than that of porcine serum (2.9 X 10(-3) M), reflecting a distinct, compartmentalized microenvironment, isolated from the circulating blood. Another significant finding was that the ionic calcium activity (5.3 X 10(-5) M) in the enamel fluid was one order of magnitude lower than the total Ca concentration. The averaged results of other determinations were: pH, 7.26; total [P], 3.9 mM; [Mg2+], 0.8 mM; [Na+], 140 mM; [K+], 20 mM; [Cl-], 150 mM; [F-], 5 X 10(-3) mM; and osmolality of the fluid, 312 mosmol/kg H2O (in the same range as that of the serum, 310 mosmol/kg H2O). The apparent electrical unbalance of the analytical data, 8.65 meq excess of positive charges, was ascribed to the presence of HCO3- in the fluid; the computed ionic strength was 164 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydrofluoric and nitric acid transport through lipid bilayer membranes

Hydrofluoric and nitric acid transport through lipid bilayer membranes were studied by a combination of electrical conductance and pH electrode techniques. Transport occurs primarily by nonionic diffusion of molecular HF and HNO3. Membrane permeabilities to HF and HNO3 ranged from 10(-4) to 10(-3) cm . s-1, five to seven orders of magnitude higher than the permeabilities to NO-3, F- and H+. Our results are consistent with the hypothesis that F- transport through biological membranes occurs mainly by nonionic diffusion of HF. Our results also suggest that of the two principal components of 'acid rain', HNO3 may be more toxic than H2SO4.

Metabolic ability and enflurane defluorination in surgical patients

Antipyrine clearance and half-life, which are measures of the hepatic metabolic ability, were determined prior to anaesthesia in 14 surgical patients. The antipyrine results correlated neither with the highest serum fluoride concentrations nor with the fluoride excretion in urine following administration of enflurane. Enzyme induction may therefore have little influence on enflurane metabolism in man. Inorganic fluoride concentrations in serum and in excreted urine were determined following the exposure of a total of 21 surgical patients to measured doses of enflurane. In the group of 14 patients tested for metabolic ability, a mean dose of 0.4 end-tidal vol. % X h enflurane resulted in a mean peak serum fluoride concentration of 6.8 mumol/l (maximum 13.6 mumol/l) 2 h after enflurane exposure. In the material as a whole, the enflurane dose was positively correlated with both post-anaesthetic highest serum fluoride concentrations and the 24-h post-anaesthetic urine pH (P less than 0.01) as well as urinary volume and fluoride excretion in urine during that time. At a urinary pH below 5.0, the fluoride excretion was very low, while the highest excretions were associated with a urinary pH of about 7.0. Raising the patient's per- and post-anaesthetic urine pH and maintaining a good urinary output (which also tends to increase urine pH) may be enough to prevent accumulation of inorganic fluoride in the body following enflurane anaesthesia.

Fluoride pharmacokinetics during acid-base balance changes in man

Five healthy subjects were each given fluoride 3.0 mg (F) as sodium fluoride tablets on two occasions - during production of acid urine, induced by giving NH4Cl, and during production of alkaline urine obtained by giving NaHCO3. Frequent plasma and urine samples were taken up to 12 h and were analyzed with a F- sensitive electrode. Control experiments without F administrations were also performed to permit calculation of net F concentration in plasma and urine. The urine F excretion was lower during acid than alkaline diuresis. Pharmacokinetic analysis of the net plasma F concentrations showed that the apparent plasma half-life of F was longer when urine was acid (4.3 +/- 0.6h: SD; n = 5) than when it was alkaline (2.4 +/- 0.4h). This could be explained by changes in the renal clearance of F, which was always lower with an acid (61.5 +/- 8.1 ml/min) than an alkaline (97.8 +/- 10.4 ml/min) urine. The apparent extra-renal clearance, which mainly represents clearance to the bone-pool, was also significantly higher during production of alkaline (109.2 +/- 20.2 ml/min) than of acid (86.3 +/- 21.3 ml/min) urine. It is suggested, that increased reabsorption of non-ionic hydrogen fluoride (HF) is responsible for the decreased renal clearance during acidic conditions.

Renal fluoride excretion during and after enflurane anaesthesia: dependency on spontaneous urinary pH-variations

Renal function, fluoride formation and excretion were studied in seven patients during and after enflurane anaesthesia and surgery. The mean maximal plasma level of fluoride was 17.4 microM. It was reached 2 h after termination of anaesthesia. Pre-operatively, fraction fluoride clearance (CF/CIn) was 0.31. During anaesthesia and surgery it decreased to 0.10 and postoperatively rose to 0.55 and 0.77 during two consecutive measurement periods. There was a highly significant correlation (P less than 0.001) between this increase in CF/CIn and the simultaneous rise in urinary pH between the two periods (r = 0.91).