Arsenic reduced the abundance of CFTR in cell lysates of opercular membranes. There was no change in CFTR cell lysates (which include cell membrane and intracellular CFTR) in control fish. A) Summary of data. Fish were adapted to freshwater (FW) for two weeks, then exposed to arsenic (12,000 ppb) or vehicle for 48 hours and then placed in seawater (SW) containing arsenic (12,000 ppb) or vehicle for 1 hr, 3 hr, and 8 hr. After the indicated times, opercula were isolated and the amount of CFTR in control (hatched bars) and arsenic treated fish (solid bars) were measured as described in methods. Data presented as percent of time 0 data. N=7/group. *P<0.05 versus FW. B) Representative Western blots of CFTR.