UPTAKE OF HGCL2 AND MEHGCL IN AN INSECT-CELL LINE (AEDES-ALBOPICTUS C6 36)/

We studied the uptake mechanism of mercuric chloride (Hg) and methylme rcuric chloride (MeHg) in Aedes albopictus C6/36 cells, The uptake kin etics, together with the effect of temperature and a metabolic inhibit or (2,4-dinitrophenol) on the mercury accumulation, were examined, Bot h amounts of internalized Hg and MeHg increased linearly with the extr acellular concentration. Initially, the influx rate was high for both metal species but MeHg was found to accumulate seven times faster than Hg, At longer exposure times it leveled off for Hg, while for MeHg, t he intracellular concentration decreased. Hg toxicity was not signific antly influenced by elevated temperatures; in contrast there was a mar ked decrease of the LC,,,,, value for MeHg. On the other hand, Hg accu mulation was temperature dependent but MeHg was not, The different tox icity and uptake rate of both mercury compounds can be explained in te rms of membrane permeability and target site. For Hg the main target s eems to be the plasma membrane, while MeHg readily crosses this barrie r and reacts with intracellular targets. 2,4-Dinitrophenol had no effe ct on the accumulation of Hg but that of MeHg was doubled, This increa sed MeHg accumulation might be the result of the inhibition of an acti ve MeHg efflux mechanism; this is in agreement with the MeHg influx ki netics. Despite these differences between Hg and MeHg, which probably result from their physicochemical properties, our experiments indiate that, for both mercury species, simple diffusion is probably the main way of entrance in Aedes cells. (C) 1998 Academic Press.