Differential Responses to Environmental Stress and Arsenic Exposure in Two Populations of Fundulus heteroclitus

Abstract

Arsenic is a dangerous, life-threatening toxicant. It is present in the drinking water of many Americans at low levels. Little is known about the health effects of chronic, low-dose exposure to arsenic. In this study, the Atlantic estuarine killifish, Fundulus heteroclitus, was used as a model to examine the effect of arsenic on a basic biological process: osmoregulation. Estuarine fish acclimate to varying salinities involves ion and water channel regulation. While a number of studies have examined the acclimation from freshwater (FW) to seawater (SW), none have examined acclimation in the other direction or studied the effect of arsenic on this process. In this study, I tested the hypothesis that transfer from seawater to freshwater, in the presence of arsenic (100ppb), will disrupt mRNA expression and protein abundance of four target proteins: CFTR, AQP-3, NKCC, and NaK-ATPase. Seawater-adapted killifish from two separate sub-populations were exposed to arsenic (48h) and then moved to freshwater. Our results demonstrate treatment with low-dose arsenic has differential and selective effects on the two sub-populations of killifish. Protein expression patterns in response to osmotic stress and arsenic exposure differed among each sub-population. We propose that genetic differences between the two sub-populations have a greater effect than arsenic exposure upon expression of the four proteins studied here.