Thimerosal positivities: patch testing to methylmercury chloride in subjects sensitive to ethylmercury chloride

• Published in: Contact dermatitis Vol. 40; no. 1; pp. 8 - 13
• Main Authors: Santucci, B., Cannistraci, C., Cristaudo, A., Camera, E., Picardo, M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.1999; Blackwell
• Subjects: Adult; alkyl mercury compounds; allergic contact dermatitis; Biological and medical sciences; Chlorides - administration & dosage; Cysteine - administration & dosage; Dermatitis, Allergic Contact - diagnosis; Dermatitis, Allergic Contact - etiology; divalent ions; Drug toxicity and drugs side effects treatment; Ethylmercuric Chloride - adverse effects; ethylmercury chloride; Female; Glutathione - administration & dosage; Humans; Irritants - adverse effects; Male; Medical sciences; metal-lothioneins; methylmercury chloride; Methylmercury Compounds - adverse effects; Miscellaneous (drug allergy, mutagens, teratogens...); Organomercury Compounds; patch test standard series; Patch Tests; Pharmacology. Drug treatments; SH groups; Sulfhydryl Compounds - adverse effects; thimerosal; Thimerosal - adverse effects; Zinc Compounds - administration & dosage; Zinc Sulfate - administration & dosage; Human; Immunopathology; Allergy; Skin disease; Thiomersal; Toxicity; Thiohydroxyl group; Crossed allergy; Preservative; Contact dermatitis; Mercury Organic compounds; Mechanism of action; Patch; Skin test
• ISSN: 0105-1873; 1600-0536
• DOI: 10.1111/j.1600-0536.1999.tb05969.x

The aim of this paper was to evaluate whether methylmercury chloride (MeHgCl) aq., when patch tested in a group of thimerosal‐positive subjects reacting to ethylmercury chloride (EtHgCl), might be a reliable model for the better understanding of interactions between alkylmercury compounds and the skin. 19 out of 21 consecutive patients who previously had given positive patch‐test reactions to both ethylmercury chloride 0.0165% eth.(EtHgCl, 0.615 mM) and MeHgCl 0.031% aq.(1.23 mM), and negative reactions to thiosalicylic acid 0.05% (3.24 mM) aq./eth. 50/50, were repatch tested to 8 μl of MeHgCl 0.031% aq. and to 8 μl of aq. solutions containing MeHgCl mixed with cysteine, glutathione, ZnSO4, Mg SO4, Mn SO4, ZnCl2, MgCl2 and Mn Cl2, respectively. The results showed that cysteine, glutathione and Zn(II) salts were able to abolish the positive reactions, demonstrating the rôle played by both thiol groups and Zn(II) itself. Patch tests concomitantly carried out in 16 out of 19 patients to 8 μl of aqueous MeHgCl and to 8 μl of aqueous solutions containing MeHgCl and MeHgCl mixed to fragment 56‐61 of metallothionein I (MT I), MT I and MT II‐Zn, respectively, revealed that all the MTs tested were able to reduce or to inhibit the reactions, demonstrating the effect of the thiol groups. Due to the close chemical similarities to EtHgCl and to its water solubility, MeHgCl seems to be a suitable model for evaluating the reactivity of alkylmercury compounds in the skin. We speculate that both EtHg‐ and MeHg‐derivatives are xenobiotics with similar reactivity. However, the lack of clinical relevance of the reactions to both alkyl compounds lead us to conclude that, since environmental exposure does not seem to play a pivotal rôle, they probably have mostly to do with compounds included in in the standard series, and are elicited by reduced function of physiological SH chelators.