INTERACTION OF CADMIUM AND BENZO[A]PYRENE IN MUMMICHOG (FUNDULUS-HETEROCLITUS) - EFFECTS ON ACUTE MORTALITY

Mummichog (Fundulus heteroclitus), a common estuarine fish species, we re exposed to cadmium (Cd) and benzo[a]pyrene (BP) to study the effect s of single and combined exposure on acute mortality. Experiments were performed to establish acute, 14 day LD50 values for Cd and BP after intraperitoneal injection. Combinations of 5.6-56 mg kg(-1) BP and 0.1 -10 mg kg(-1) Cd were injected concomitantly to investigate interactiv e effects on mortality. The calculated LD50 value for BP was 35.7 mg k g(-1) (95% confidence interval (c.i.): 29.3-43.6), the LD50 value for Cd was 6.5 mg kg(-1) (95% c.i.: 4.4-9.5). Based on the LD50 values, to xic units were calculated for the combined dosages of Cd and BP. The r esults showed that when Cd was dosed at sublethal levels together with lethal BP doses, mortality was lower than expected. When BP was dosed at sublethal levels with sublethal Cd doses, mortality was higher tha n expected. These results indicate that, depending on the concentratio ns of the compounds, both synergistic and antagonistic effects can occ ur when mummichog are exposed to a combination of Cd and BP. Possible mechanisms for these interactive effects may include the inhibition of P450 by Cd and the inactivation of metallothioneins by reactive BP me tabolites. (C) 1998 Elsevier Science Ltd. All rights reserved.