METHYLMERCURY DECREASES IL-1-BETA IMMUNOREACTIVITY IN THE NERVOUS-SYSTEM OF THE DEVELOPING FROG XENOPUS-LAEVIS

In aquatic ecosystems, mercury can become methylated and act as a pote nt environmental toxin, producing developmental and neurotoxic effects in a variety of species, including frogs. Molecular indicators provid e a means of assessing exposure to methylmercury and for understanding how it and other environmental toxins alter cellular function. Molecu les such as growth or survival factors, and cytokines are good candida tes for molecular indicators of exposure and/or damage because they ar e intimately related to cell and molecular processes that underlie nor mal growth and function. The cytokine, IL-1 beta, was measured in whol e frog embryos using Western blot methods and in specific structures u sing immunocytochemistry after exposure to 0, 10, 25, 50 and 100 parts per billion (ppb) methylmercury chloride (mmc). We observed no signif icant changes in total IL-1 beta in whole embryo extracts. However, st atistically significant decreases in IL-1 beta were observed in the Vt h cranial ganglion and myotomal blocks of Xenopus laevis embryos expos ed to concentrations greater than or equal to 50 ppb mmc. In addition, increased mortality and alterations in gross morphology and behavior were altered by these same concentrations of mmc. Thus, frog embryos a re highly susceptible to low levels of mmc contamination, and IL-1 bet a is an indicator of mmc exposure in the nervous system. (C) 1997 Into x Press, Inc.