Flow-cytometric analysis on cytotoxic effect of thimerosal, a preservative in vaccines, on lymphocytes dissociated from rat thymic glands

• Published in: Toxicology in vitro 2005-03, Vol.19 (2), p.191-198
• Main Authors: Ueha-Ishibashi, T., Oyama, Y., Nakao, H., Umebayashi, C., Hirama, S., Sakai, Y., Ishida, S., Okano, Y.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis - drug effects; Calcium - metabolism; Cell death; Cell Separation; Cell Survival - drug effects; Cytotoxicity; Dose-Response Relationship, Drug; Flow Cytometry - methods; Immunization; Intracellular Membranes - drug effects; Lymphocytes; Lymphocytes - drug effects; Lymphocytes - metabolism; Lymphocytes - pathology; Preservatives, Pharmaceutical - toxicity; Rats; Rats, Wistar; Thimerosal; Thimerosal - toxicity; Thymus Gland - cytology; Vaccines - adverse effects
• ISSN: 0887-2333; 1879-3177
• DOI: 10.1016/j.tiv.2004.07.004

There is a concern on the part of public health community that adverse health consequence by thimerosal, a preservative in vaccines for infants, may occur among infants during immunization schedule. Therefore, the cytotoxic action of thimerosal was examined on lymphocytes dissociated from thymic glands of young rats using a flow cytometer and respective fluorescent probes for monitoring changes in intracellular Ca 2+ concentration ([Ca 2+]i) and membrane potential, and for discriminating intact living cells, apoptotic living cells and dead cells. Incubation with thimerosal at 3 μM or more (up to 30 μM) for 60 min depolarized the membranes, associated with increasing the [Ca 2+]i. Thimerosal at 30 μM induced an apoptotic change in membranes of almost all living cells. Furthermore, the prolonged incubation with 30 μM thimerosal induced a loss of membrane integrity, leading to cell death. Since the blood concentration of thimerosal after receiving vaccines is theoretically submicromolar, it may be unlikely that thimerosal affects lymphocytes of infants.