Arsenic Affects Muscle Development and Structure in Fundulus Heteroclitus

Arsenic is a naturally occurring metalloid that can enter rivers and ground water. Epidemiological studies have correlated arsenic exposure with adverse developmental outcomes such as low birth weight, delays in the use of musculature, and altered locomotor activity. Previously in our lab, embryonically exposed killifish (Fundulus heteroclitus) were found to have changes in muscle development. Microarray analysis showed several genes involved in muscle development and formation altered and histological analysis showed an increase in small muscle fiber size. In this study, killifish were used to help understand if changes in muscle formation and fiber density after embryonic exposure persist, are exacerbated, or lessen during an arsenic exposure regime typical of humans. Killifish embryos were exposed to concentrations of arsenic ranging from 0-5000 ppb. Upon hatching the juveniles were split and transferred into either clean water or continued receiving the same arsenic exposure. Samples were collected at 0, 2, 4, 8, and 16 weeks of juvenile development. Arsenic exposure resulted in significant decreases in weight and lengths of both embryonic only exposed juveniles as well as continuously exposed juveniles between 4 and 16 weeks of development at concentrations as low at 800 ppb. An increase in small muscle fiber size was also seen in a dose dependent manner for both groups of embryonic only and continuous exposures between 4 and 16 weeks of juvenile development. Together these findings indicate that low concentration arsenic exposure during just embryogenesis, or with a continuous exposure throughout juvenile development, can lead to significant changes in growth and muscle formation