Effect of Cys, GSH, and pH on Mercury Release from Tibetan Medicine Zuotai, ß-HgS, and α-HgS in Artificial Gastrointestinal Juices.

Zuotai, also named as "gTso thal", a known Tibetan medicinal mixture containing insoluble cubic crystal mercuric sulfide (ß-HgS), has been used to treat diseases with long history. The mercury release ratio from Zuotai in gastrointestinal environment is one determinant factor for its bioavailability and biological effect. However, the information is still scarce now. Therefore, the study was designed to investigate the effect of sulfhydryl biomolecules [L-cysteine (Cys) and glutathione (GSH)] and pH on mercury dissociation from Zuotai, ß-HgS, and hexagonal crystal mercuric sulfide (α-HgS) in artificial gastrointestinal juices or pure water with a 1:100 solid-liquid ratio. And, the digestion and peristalsis of gastrointestinal tract were simulated in vitro. The results showed the following trend for the mercury release ratio of Zuotai, artificial gastric juice > artificial intestinal juice > pure water, whereas the trend for ß-HgS and α-HgS was as follows, artificial intestinal fluid > artificial gastric fluid > pure water. The mercury release ratios of Zuotai, ß-HgS, and α-HgS significantly increased in artificial intestinal juice containing L-Cys or GSH compared to those without sulfhydryl biomolecules in the juice. However, in contrast to the results observed for ß-HgS and α-HgS, the mercury release ratio of Zuotai was reduced remarkably in pure water and artificial gastric juice with Cys or GSH. And, we found that strong acidic or strong alkaline environments promoted the dissociation of mercury from Zuotai, ß-HgS, and α-HgS. Taken together, current findings may contribute to other studies regarding clinical safety and bioavailability of the traditional drug Zuotai containing ß-HgS.

Mercury species, selenium, metallothioneins and glutathione in two dolphins from the southeastern Brazilian coast: Mercury detoxification and physiological differences in diving capacity.

In the present study, the concentration of trace elements, total mercury (Hg) and selenium (Se) and mercury forms (MeHg, Hginorg and HgSe) in the vulnerable coastal dolphins Pontoporia blainvillei and Sotalia guianensis were appraised and compared, using metallothioneins (MT) and glutathione (GSH) as biomarkers for trace element exposure. The trace element concentrations varied between muscle and liver tissues, with liver of all dolphin specimens showing higher Hg and Se concentrations than those found in muscle. Hg, MeHg and Hginorg molar concentrations showed a clear increase with Se molar concentrations in the liver of both dolphins, and Se concentrations were higher than those of Hg on a molar basis. Se plays a relevant role in the detoxification of MeHg in the hepatic tissue of both dolphins, forming Hg-Se amorphous crystals in liver. In contrast, MT were involved in the detoxification process of Hginorg in liver. GSH levels in P. blainvillei and S. guianensis muscle tissue suggest that these dolphins have different diving capacities. Muscle Hg concentrations were associated to this tripeptide, which protects dolphin cells against Hg stress.

[Overview of studies on detoxification effect of smilacis glabrae rhizoma on mercury poisoning].

Mercury-containing preparations are widely used in surgery department of traditional Chinese medicine and have made remarkable achievements. But they are toxic to human kidney, nerve, immune, etc. Smilacis Glabrae Rhizoma is sweet, tasteless and neutral in nature and able to enter liver and stomach channels and detoxify mercury poisoning. This article summarizes the mercury poisoning and the detoxification effect of Smilacis Glabrae Rhizoma in ancient records, pharmaceutical studies and clinical application, in order to provide ideas and methods for the safe use of mercury-containing preparations in surgery department of traditional Chinese medicine.

Induction by mercury compounds of metallothioneins in mouse tissues: inorganic mercury accumulation is not a dominant factor for metallothionein induction in the liver.

Among the naturally occurring three mercury species, metallic mercury (Hg(0)), inorganic mercury (Hg(II)) and methylmercury (MeHg), Hg(II) is well documented to induce metallothionein (MT) in tissues of injected animals. Although Hg(0) and MeHg are considered to be inert in terms of directly inducing MT, MT can be induced by them after in vivo conversion to Hg(II) in an animal body. In the present study we examined accumulations of inorganic mercury and MT inductions in mouse tissues (brain, liver and kidney) up to 72 hr after treatment by one of three mercury compounds of sub-lethal doses. Exposure to mercury compounds caused significant mercury accumulations in mouse tissues examined, except for the Hg(II)-treated mouse brain. Although MeHg caused the highest total mercury accumulation in all tissues among mercury compounds, the rates of inorganic mercury were less than 10% through the experimental period. MT inductions that depended on the inorganic mercury accumulation were observed in kidney and brain. However, MT induction in the liver could not be accounted for by the inorganic mercury accumulation, but by plasma IL6 levels, marked elevation of which was observed in Hg(II) or MeHg-treated mouse. The present study demonstrated that MT was induced in mouse tissues after each of three mercury compounds, Hg(0), Hg(II) and MeHg, but the induction processes were different among tissues. The induction would occur directly through accumulation of inorganic mercury in brain and kidney, whereas the hepatic MT might be induced secondarily through mercury-induced elevation in the plasma cytokines, rather than through mercury accumulation in the tissue.

Attenuation by methyl mercury and mercuric sulfide of pentobarbital induced hypnotic tolerance in mice through inhibition of ATPase activities and nitric oxide production in cerebral cortex.

This study is aimed at exploring the possible mechanism of hypnosis-enhancing effect of HgS or cinnabar (a traditional Chinese medicine containing more than 95% HgS) in mice treated with pentobarbital. We also examined whether the effect of HgS is different from that of the well-known methyl mercury (MeHg). After a short period (7 days) of oral administration to mice, a nontoxic dose (0.1 g/kg) of HgS not only significantly enhanced pentobarbital-induced hypnosis but also attenuated tolerance induction; while a higher dose (1 g/kg) of HgS or cinnabar exerted an almost irreversible enhancing effect on pentobarbital-hypnosis similar to that of MeHg (2 mg/kg) tested, which was still effective even after 10 or 35 days cessation of administration. To study comparatively the effects of different mercury forms from oral administration of MeHg and HgS on membrane ATPase activities of experimental mice, analysis of the Hg content in the cerebral cortex revealed that correlated with the decrease of Na(+)/K(+)-ATPase and Ca(2+)-ATPase activities. Furthermore, NO levels of blood but not that of cerebral cortex were also decreased by mercuric compounds. Although pentobarbital alone enhanced cytochrome p450-2C9 in time dependent manner, all of mercurial compounds tested had no such effect. All of these findings indicated that the mercurial compounds including cinnabar, HgS and MeHg exert a long-lasting enhancing hypnotic activity without affecting pentobarbital metabolism, which provides evidence-based sedative effect of cinnabar used in Chinese traditional medicine for more than 2,000 years. The nontoxic HgS dosing (0.1 g/kg/day) for consecutive 7 days is perhaps useful for delaying or preventing pentobarbital-tolerance.

Neurotoxicological effects of cinnabar (a Chinese mineral medicine, HgS) in mice.

Cinnabar, a naturally occurring mercuric sulfide (HgS), has long been used in combination with traditional Chinese medicine as a sedative for more than 2000 years. Up to date, its pharmacological and toxicological effects are still unclear, especially in clinical low-dose and long-term use. In this study, we attempted to elucidate the effects of cinnabar on the time course of changes in locomotor activities, pentobarbital-induced sleeping time, motor equilibrium performance and neurobiochemical activities in mice during 3- to 11-week administration at a clinical dose of 10 mg/kg/day. The results showed that cinnabar was significantly absorbed by gastrointestinal (G-I) tract and transported to brain tissues. The spontaneous locomotor activities of male mice but not female mice were preferentially suppressed. Moreover, frequencies of jump and stereotype-1 episodes were progressively decreased after 3-week oral administration in male and female mice. Pentobarbital-induced sleeping time was prolonged and the retention time on a rotating rod (60 rpm) was reduced after treatment with cinnabar for 6 weeks and then progressively to a greater extent until the 11-week experiment. In addition, the biochemical changes in blood and brain tissues were studied; the inhibition of Na(+)/K(+)-ATPase activities, increased production of lipid peroxidation (LPO) and nitric oxide (NO) were found with a greater extent in male mice than those in female mice, which were apparently correlated with their differences in the neurological responses observed. In conclusion, these findings, for the first time, provide evidence of the pharmacological and toxicological basis for understanding the sedative and neurotoxic effects of cinnabar used as a Chinese mineral medicine for more than 2000 years.

Differential neurotoxic effects of methylmercury and mercuric sulfide in rats.

Methylmercury (MeHg) is an environmental toxicant, while mercuric sulfide (HgS) is a main active component of cinnabar, a Chinese mineral medicine used as a sedative. Because the neurotoxicological effects of HgS were not clearly understood, in this study, we attempted to compare HgS with MeHg in various physiological responses in Sprague-Dawley rats. After oral administration (2 mg/(kg day)) for consecutive 5 and 14 days, MeHg reversibly decreased both of motor nerve conduction velocity (MNCV) and tail flick response, whereas irreversibly inhibited all of the motor equilibrium performance, recovery of compound muscle action potentials (CMAP) following exhaustic tetanic stimuli and Na+/K+-ATPase activity of the isolated sciatic nerve. These toxic effects of MeHg were found in well correlation of Hg contents of various tissues (blood, cerebral cortex, liver and kidney) in rats. For comparison, a dose of 1g/(kg day) of HgS was orally administered to the rats based on our previous findings on ototoxicity of HgS. The results revealed that HgS only reversibly delayed the recovery of suppressed CMAP and inhibited sciatic nerve Na+/K+-ATPase activity in accordance to the lower Hg contents of the tissues. These findings provide the important information on the differential susceptibility of various nervous tissues to MeHg and HgS. The neruotoxic effects produced by HgS was estimated to be about 1000 of those induced by MeHg found in this study and our previous reports.

Neurotoxicity of mercury sulfide in the vestibular ocular reflex system of guinea pigs.

A traditional Chinese mineral medicine, cinnabar, naturally occurring mercuric sulfide (HgS), is still occasionally prescribed, but the neurotoxic effects of HgS have not been elucidated. In this paper, an animal model of the purified HgS intoxication was established in guinea pigs in order to study neurotoxicity and pathophysiology of the vestibular ocular reflex system (VOR). Guinea pigs were dosed with HgS by gastric gavage (0.01, 0.1 and 1.0 g/kg per day) for 7 consecutive days. By means of caloric testing coupled with the electronystagmographic (ENG) recording in guinea pigs, we have found that HgS at a dose of 0.1 g/kg induced reversible caloric hypofunction pattern and at a higher dose of 1.0 g/kg induced irreversible hypofunction of caloric test. Monitoring the mercury contents of various tissues (blood, kidney, liver and cerebellum) by continuous flow and cold vapor atomic absorption spectrometry (AAS) revealed that a certain amount of HgS could be absorbed from the gastrointestinal tract and was detectable in these tissues. In addition to the induced dysfunction of VOR system, HgS also caused disturbance of motor performance in guinea pigs. In enzyme assay, Na+/K+-ATPase activity of cerebellum was also significantly inhibited by HgS. Morphological studies showed partial cell loss only in the cerebellar Purkinje cell layer, but not in the granule cell layer, nor in the vestibular labyrinth. All of these findings suggest that cerebellar Purkinje cells are the sensitive target site responsible for HgS-inducing dysfunctions of both VOR system and the motor performance in guinea pigs. Thus, it is concluded that caloric test coupled with ENG recording in VOR system is certainly a sensitive biomarker for monitoring the neurotoxicity of HgS.

Cytotoxicity of mercury compounds in LLC-PK1, MDCK and human proximal tubular cells.

Six mercury compounds [HgCl2 (MC), Hg(CH3COO)2 (MA), Hg(NO3)2 (MN), C2H5HgSC6H4COONa (EMT), C6H5HgOCOCH3 (PMA) and CH3CIHg (MMC)] were studied using two kidney cell lines (MDCK and LLC-PK1), primary cultures of human proximal tubular cells (hPTC) and nonrenal cell lines (SAOS and Hep G2). Cell damage was measured with four different tests: neutral red uptake, mitochondrial dehydrogenase activity (MTT conversion), thymidine incorporation and protein content. Relative toxicity was established by the determination of the concentration of test compound inducing a 50% reduction of the parameter considered (EC50 value). Two groups could be distinguished: PMA, EMT and MMC are one order of magnitude more toxic than MC, MN and MA. Cellular uptake was measured by the HPLC-hybrid generation AAS after 24 hours treatment with 1.5 microM MC, MMC, PMA or EMT in MDCK cells, revealing Hg concentrations of 42.8 +/- 2.5 ng/mg protein for MC, 596.9 +/- 87.8 ng/mg protein for MMC, 269.8 +/- 75.7 ng/mg protein for PMA and of 115.9 +/- 25.2 ng/mg protein for EMT. Cytotoxicity was positively correlated with cellular uptake. The effect of the cellular GSH content on the toxicity of mercury was studied using the GSH synthesis inhibitor L-buthionine sulfoximine (BSO). In all cases an enhanced cytotoxicity was observed after BSO treatment. 2-Oxo-4-thiazolidine carboxylic acid (OTC) was used as a substrate for the GSH synthesis. Although OTC did not enhance the GSH content, the cytotoxicity of MC, MN and MA decreased significantly, no changes were observed for the other mercurials.(ABSTRACT TRUNCATED AT 250 WORDS)