Effect of kidney damage on the mobilisation of mercury by thiol-complexing agents

ABSTRACT Mobilisation of mercury by thiol-complexing agents is the accepted treatment for chronic mercury intoxication. The success of such treatment is judged by the urinary excretion of mercury which might be modified by existing kidney damage caused either by the mercury itself or by other factors. In the present work the ability of three thiol-complexing agents, D-penicillamine, N-acetyl-D, L-penicillamine, and 2,3-dimercaptosuccinic acid (DMSA) to remove mercury from a damaged kidney and to increase the urinary excretion of mercury were studied. Kidney damage was induced by the injection of 20 mg/kg sodium chromate three days before the injection of 2·5 μmoles/kg HgCl₂ or three and seven days before the administration of a similar dose of mercury complexed with D-penicillamine. It was shown that both renal uptake and urinary excretion of mercury were decreased in animals with damaged kidneys. This effect lessened with time between the induction of damage and the injection of mercury-penicillaminate. Each of the three chelating agents was given 48 and 54 hours after the administration of HgCl₂ in equivalent (400 μmoles/kg) doses. All were able to remove mercury from the kidneys, but DMSA was far the most effective and only DMSA increased the urinary excretion of mercury. The amount of mercury removed from the kidneys by the chelators was less in animals with renal damage than in controls, but the difference was insignificant if renal mercury depletion was related to the initial renal mercury content.

Antitrypanosomal activity of trivalent antimonials in vitro and its significance

The SbIII preparations available for clinical use were compared in vitro for their concentration/time/effect curves on Trypanosoma venezuelense (T. evansi), measuring decrease of motility and of parasite numbers. With these two criteria leading to similar relative results, the drugs are classified into a rapidly acting group, led by sodium emetic (AST), followed by its dimethylcysteine chelate (NAP) and Anthiomaline, and a less and more slowly acting one: Triostam, Astiban and Stibophen. The relative activity of these drugs in vitro is parallel to that encountered against Schistosoma mansoni, attributed to a similar pattern of intracellular absorption. In vivo effectiveness may depend on bioavailability of Sb in the host and the direct action on the parasite, reflected by its in vitro activity. The interplay of these two factors leads to a different in vitro/in vivo activity relationship of the antimonials even in the same host (mouse) and to its variation in other host species.

The effect of penicillamine and 2,3-dimercaptosuccinic acid on urinary excretion and tissue distribution of gold

In order to study interactions in vivo between Au+ and SH-containing agents, groups of mice were given 35 mumol/kg of radiolabelled [195Au] thiomalate (Myocrisin) intramuscularly. The administration of Myocrisin is known to result in protein-bound gold and free thiomalate (mercaptosuccinate). High doses of dimercaptosuccinate (1 mmol/kg daily) increased the urinary excretion of radiolabelled gold [195Au] for several days. Treatment for 7 days with 1 mmol/kg of penicillamine or dimercaptosuccinate reduced the blood and kidney levels of gold to 30--50% of the controls. The oral administration of penicillamine in high doses, 1--10 mmol/kg, increased significantly the urinary excretion of [195Au] the first day after the Myocrisin injection, but on the subsequent days the radio-metal excretion was unaffected by the treatment. A lower dose level of penicillamine (0.3 mmol/kg daily) gave rise to only a small and insignificant increase in the urinary excretion of gold. The present results indicate that penicillamine at low clinical doses is an inefficient chelator of gold, while high doses (presumably comparable to about 1 200 mg daily in humans) may mobilize certain amounts of the metal deposits.

Pharmacodynamics of stannous chelates administered with 99mTc-labeled chelates

The pharmacodynamics of several tin compounds were studied in healthy rabbits, rabbits with myocardial infarcts, and isolated myocardial tissue. The results showed that tin chelates of pyrophosphate, HEDP, DTPA, and glucoheptonate are very unstable in vivo, giving rise to free stannous ions. These ions localize mainly in bone, with the rest being primarily excreted in the urine. They also concentrate more in infarcted than in normal myocardium; there they enter the mitochondria. The supernatant of homogenates contains bound and free fractions, demonstrating a subcellular distribution pattern similar to that of calcium ions. Tin chelates have different pharmacodynamics from the corresponding 99mTc chelates.

Effect of endogenous and exogenous prostaglandin E on Friend erythroleukaemia cell growth and differentiation

The effect of exogenous and endogenous prostaglandins on the patterns of growth and differentiation of Friend erythroleukaemia cells (FLC) were studied. During the differentiation process, DMSO stimulated PGE synthesis by an average of 95%. The addition of a long-acting synthetic analogue of PGE2,16,16-dimethyl-PGE2-methyl ester (di-M-PGE2) to the culture medium only slightly and temporarily slowed cell growth, with no appreciable induction of differentiation. However, in the presence of DMSO, the same concentration of di-M-PGE2 produced 73% inhibition of cell growth and accelerated and potently stimulated haemoglobin production. The action of both di-M-PGE2 and DMSO on cell proliferation was dependent upon the state of cell growth at the time of the administration of these compounds. FLC cultures treated with DMSO + di-M-PGE2 produced considerable amounts of haemoglobin before even one duplication cycle was completed. Both DMSO and di-M-PGE2 stimulated endogenous PGE biosynthesis, and the biosynthetic effect of these compounds was synergistic. Inhibition of endogenous prostaglandin synthesis by indomethacin completely abolished the effects produced by DMSO + di-M-PGE2 on the growth, and substantially reduced the stimulated differentiation of FLC. These data suggest that an endogenously synthesized prostaglandin plays a significant role in both the inhibition of replication and in the stimulation of differentiation induced by DMSO and di-M-PGE2 in Friend erythroleukaemia cells.

The pharmacology of 2,3-dimercaptosuccinic acid and its potential use in arsenic poisoning

Arsenic (As2O3)-poisoned rats were treated with either 2,3-dimercaptosuccinic acid (DMS) or dimercaptopropanol (BAL) at doses of 30 mg/kg/day. A control group received no treatment. The total quantity of arsenic excreted was not significantly different in response to 4 days of treatment with either DMS or BAL. In addition, there was no difference between the two drug treatment groups in the residual arsenic content of brain, liver, kidney and spleen after treatment. Both drugs reduced the arsenic content of each tissue to approximately 40% of that of untreated controls. Previous studies have shown that DMS is orally effective for the treatment of lead poisoning. The LD50 of DMS was determined to be in excess of 3 g/kg in rats and mice, approximately 30 times the LD50 of BAL. No gross, histopathological or biochemical evidence of toxicity was observed in mice, rats or dogs which received DMS 5 days per week for 6 months. DMS did not affect the excretion of zinc, iron, calcium or magnesium. Urinary copper excretion was significantly elevated in response to 30 mg/kg of DMS, suggesting that the drug might also be useful for the treatment of Wilson's disease.

Reduction of methylmercury concentration in neonatal rat brains after administration of dimercaptosuccinic acid to dams while pregnant

Sprague-Dawley rats were gavaged on day 7 of gestation with 1.62, 3.23 or 10 mg methylmercury/kg. Beginning one day later, the dams were administered 0, 20 or 40 mg 2,3-dimercaptosuccinic acid/kg/day until they delivered their pups. Concentrations of methylmercury in the brains of pups whose dams were treated with 20 mg DMSA/kg/day were reduced 50% compared with control pups. 40 mg DMSA/kg/day decreased brain concentrations 70% compared to non-chelated controls. The data indicate that DMSA might be effective in protecting the developing organism against morphological and/or behavioral teratological consequences of methylmercury poisoning in utero.

2,3-Dimercaptosuccinic acid: a new agent for the treatment of lead poisoning

Using minimally lead-poisoned rats, we have measured urinary and fecal lead excretion in response to 2,3-dimercaptosuccinic acid (DMS) administered i.p. or p.o. and compared it to that induced by dimercaptopropanol (BAL) (i.p.), EDTA (i.p.), D-penicillamine (p.o. and i.p.) and the combination of BAL and EDTA (i.p.). At doses of 30 mg/kg, parenterally administered DMS was as effective as i.p. BAL and these two drugs were more effective than the other treatment groups. However, p.o. DMS was only 20% less effective and was as effective as i.p. EDTA and the combination of EDTA + BAL i.p. and significantly more effective than D-penicillamine p.o. or i.p. Unlike BAL, most lead excretion in response to DMS was via the urine, undoubtedly reflecting the greater water solubility of DMS. When mice were fed a diet containing both lead and DMS, the drug prevented the accumulation of porphyrins in erythrocytes. Studies with 210Pb indicate that this prophylactic effect is not due to an inhibition of lead absorption but rather to enhanced excretion of lead. The residual tissue distribution of 210 Pb administered simultaneously with DMS was not different form that of 210Pb alone. Since DMS is orally effective and its LD50 is 30 times greater than that of BAL, we expect this compound to be clinically useful in the treatment of lead poisoning.

Effect of dimercaptosuccinic acid on toxicity of Habu snake (Trimeresurus flavoviridis, Hallowell) venom

Habu venom (HV) incubated with dimercaptosuccinic acid (DMS) or thiosuccinic acid (TMA), was given subcutaneously to mice. The LD50 of HV was 19.7 mg/kg, and after treatment with TMA and DMS, it was 38.1 and 47.1 mg/kg, respectively. The logarithm concentration--mortality curve for the DMS-treated HV shifted to the right compared with the curve for crude HV. The curve for the TMA-treated HV was intermediate between these two. Decimal two mg of HV was then incubated with DMS, and such was given intramuscularly to mice. Hemorrhage and edema which occurred after administration of crude HV were markedly decreased with injection of DMS-treated HV, but the myonecrosis was not greatly affected. At 24 hr after the intramuscular dosing of 1 mg of HV into rats, lymphopenia, acute involution of lymphatic tissue, decrease in liver glycogen and lipid granules in zona fasiculata were apparent, indicating the mark of a stressor. When the DMS-treated venom was administered, the blood picture and histological findings did not differ greatly from the controls. As DMS has marked anti-HV activity, it may be used to investigate treatments for cases of Habu snake bite.