A COMPARISON OF THE DISTRIBUTION OF SOME HALIDE IONS IN THE BODY

Interaction of bromine with iodine in the rat thyroid gland at enhanced bromide intake

In experiments with rats, we have found that at enhanced intake of bromide, bromine does not replace chlorine in the thyroid; it replaces iodine. Under our experimental conditions, more than one-third of the iodine content in the thyroid was replaced by bromine. In the thyroid, bromine probably remained in the form of bromide and, in proportional to its increased concentration, the production of iodinated thyronines decreased, with the sum of the iodine and bromine concentrations being constant at the value of 20.51 +/- 1.16 mumol/g dry wt of the thyroid. In contrast to other organs, the biological behavior of bromine in the thyroid is not similar to the biological behavior of chlorine but resembles more that of iodine.

The toxicology of bromide ion

Inorganic bromide is widely distributed in nature. Its natural physiological role in animal life is unknown. More than a century ago bromide was introduced in medicine as an antiepileptic drug. Nowadays, man is primarily exposed to bromide via food as the result of use of bromide-containing fumigants in intensive horticulture and in the treatment of food stocks. In this review exposure of man to bromide is described, and the pharmacological and toxicological effects of bromide ion are discussed.

Application of whole-body autoradiography in toxicology

Whole-body autoradiography enables the drugs and toxicants to be distributed throughout the animal. Good results are obtained with this technique. However, certain artifacts can occur that could lead to misinterpretation, and these must be known. These artifacts are described. From the metabolic point of view, autoradiography provides data on the distribution kinetics of a compound and the elimination of radioactivity in various organs. These data are a guide for quantitative research into the metabolism of a compound. From the toxicological point of view, it must be admitted that the main purpose of this technique is to reveal the sites of retention of radioactivity. Such specific organ retention could be the consequence of the activation of a minor metabolite into a very reactive compound. If this is so, it is a specific organ effect which could not be studied by other techniques and could lead the way to a more specific organ effect which could not be studied by other techniques and could lead the way to a more appropriate line of research in the study of chronic toxicity. However, it must be recalled that the fact that a compound is retained by a specific organ does not always mean that the compound exerts a toxic effect upon the said organ. With this technique, distribution study can be performed on pregnant animals, and it provides us with more data concerning the transplacental passage of radioactive metabolites. All these aspects of the technique clearly indicate that whole-body autoradiography should be insisted upon during the early stages of development of new molecules. Successive experiments could then lead to selecting the best experimental conditions for metabolic pharmacokinetics and studies in toxicology.

Pharmacokinetics of bromide ion--an overview

The recent role of bromide as a residue in food and water necessitated its toxicological investigation. Although much was known already about the absorption, distribution and elimination of bromide, more data were required, especially for the rat. The pharmacokinetics in the rat were therefore investigated, with emphasis on cumulation and on the role of chloride in bromide elimination. This review recapitulates old and recent findings on the fate of bromide.

Antidote effect of sodium fluoride against organophosphate poisoning in mice

Pretreatment of mice with atropine (17.4 mg/kg) + NaF (5 or 15 mg/kg) had a significant antidotal effect over atropine alone against the lethality produced by soman and sarin. Atropine + NaF (15 mg/kg) was effective against tabun, whereas the lower dose of NaF was not. An effect of NaF on organophosphate inhibited acetylcholinesterase could not account for the antidotal action of NaF. NaF had no effect on liver somanase activity but inhibited aliesterase activity. Aliesterase activity in NaF pretreated soman-poisoned mice was significantly (p less than 0.05) higher than in those receiving atropine alone. In CBDP-pretreated mice NaF did not significantly attenuate the toxicity of soman. It is hypothesized that the antidotal effect of NaF versus organophosphate poisoning is due to its antidesensitizing action at nicotinic receptors in the neuromuscular junction and/or sympathetic ganglia in addition to the proposed increased hydrolysis of sarin and direct detoxification of tabun.

Alterations in the metabolism of fats and phosphatides in rat liver induced by halide ions

The effects of halide ions on several pathways of lipid metabolism have been investigated in rat liver slices. Through the use of carboxyl-14-C-labeled acetate and palmitate and U-14-C-labeled glycine, striking differences were found when the effects of the four halide ions on the labeling of the lipids were compared. Both fluoride and iodide dpressed [14-C]acetate incorporation into phosphatide and triglyceride fractions. The effects of the halide ions on the labeling from the effects observed when [14-C]acetate was the precursor of the lipid molecule. In contrast with the phospholipid fractions, the level of radioactivity from [14-C]palmitate incorporated into the triglycerides was lower with fluoride than with chloride. The incorporation of [14-C]glycine into the phospholipids was also greatly depressed by fluoride. The effects of halide ions on acetoacetate formation, on 14-CO2 production and on the acetylcoenzyme A synthetase of rat liver were also investigated. Decreasing [I-14-C]-acetate conversion to acetoacetate iodide had an opposite effect on 14-CO2 production from the same labeled substrate. The effects of the four halide ions and the differences observed with the three labeled substrates on several pathways related to lipid metabolism are discussed.

The oxidation of reduced nicotinamide nucleotides by hydrogen peroside in the presence of lactoperoxidase and thiocyanate, iodide or bromide

Lactoperoxidase (EC 1.11.1.7) catalysed the oxidation of NADH by hydrogen peroxide in the presence of either thiocyanate, iodide or bromide. In the presence of thiocyanate, net oxidation of thiocyanate occurred simultaneously with the oxidation of NADH, but in the presence of iodide or bromide, only the oxidation of NADH occurred to a significant extent. In the presence of thiocyanate or bromide, NADH was oxidized to NAD(+) but in the presence of iodide, an oxidation product with spectral and chemical properties distinct from NAD(+) was formed. Thiocyanate, iodide and bromide appeared to function in the oxidation of NADH by themselves being oxidized to products which in turn oxidized NADH, rather than by activating the enzyme. Iodine, which oxidized NADH non-enzymically, appeared to be an intermediate in the oxidation of NADH in the presence of iodide. NADPH was oxidized similarly under the same conditions. An assessment was made of the rates of these oxidation reactions, together with the rates of other lactoperoxidase-catalysed reactions, at physiological concentrations of thiocyanate, iodide and bromide. The results indicated that in milk and saliva the oxidation of thiocyanate to a bacterial inhibitor was likely to predominate over the oxidation of NADH.