Bone Strength and Acetylcholinesterase Inhibition as Endpoints in Chlorpyrifos Toxicity toFundulus heteroclitus

Abstract

Brain acetylcholinesterase (AChE) inhibition was measured during 4-week and 4-day episodic exposures to chlorpyrifos. Organisms were exposed to a seawater (−) control, an acetone (+) control (0.1%), and 0.625, 1.25, 2.5, 5.0, and 10.0 μg of chlorpyrifos L−1in each test. These episodic exposures significantly depressed AChE activity at 2.5, 5.0, and 10.0 μg L−1(weekly test) and at 1.25, 2.5, 5.0, and 10.0 μg L−1(daily test). Six-hour pulsed exposure to chlorpyrifos inhibited brain AChE activity at concentrations as low as 1. 25 μg L−1. Stress at failure of caudal vertebrae following episodic exposure was also tested. Analysis of samples from daily 6-h treatments found no differences after 2 days; however, vertebrae were significantly weaker (than controls) after 4 days. Analysis of weekly 6-h exposures found weaker caudal vertebrae after 2 weeks but not after 4 weeks.