Impacts of prolonged chlorpyrifos exposure on locomotion and slow-and fast- twitch skeletal muscles contractility in rats.

Nancy Hallal,Ali Salami,Mahmoud Khalil,Mohamed E Moustafa,Wiam Ramadan,Hiba El Khayat El Sabbouri,Hassan Khachfe,Wissam H Joumaa

doi:10.1016/j.toxrep.2019.06.006

Abstract

Investigate the effect of dietary exposure to chlorpyrifos on locomotion and contraction of soleus andextensor digitorum longus (edl) involved in locomotion. Methods: Rats were fed diets containing 1 or 5 mg kg-1 of chlorpyrifos for six weeks. Locomotion has been assessed weekly using beam walking and beam balance tests. Soleus and edl were removed to study contractile properties, myofibrillar protein content and myosin heavy chain isoforms. Animals treated with 5 mg kg-1 chlorpyrifos had a decrease body weight. An increase by 28% and 24% in latency time assessed by beam walking test and a decrease by 9% and 13% in the beam balance time was reported after 6 weeks of 1 and 5 chlorpyrifos exposure respectively. The contractile properties in soleus showed an increase in twitch amplitude by 25% and 63% in 1 and 5 doses respectively, without modification in the contraction time and half relaxation time. edl treated with 1 mg kg-1 showed a decrease by 35%, 42% and 22% in twitch amplitude, contraction time and half relaxation time respectively. edl treated with 5 mg kg-1 showed an increase of 23% in twitch amplitude without modification of the other parameters. These changes were associated with modification of myofibrillar protein content in all treated groups. Myosin heavy chain isoforms were altered in both skeletal muscles treated with 1 mg kg-1. Exposure to chlorpyrifos can alter the locomotion and produce physiological changes in a dose and muscle type related manner.

Highlights

Even though lots of governmental regulations are being taken to limit the market growth of chlorpyrifos (CPF) over the coming years, it remains one of the most common organophosphorus pesticides used worldwide
The aim of our study is to investigate whether the prolonged daily exposure of adolescent rats for six weeks to two different doses of CPF may affect 1) the locomotor activity assessed in vivo by the beam walking test and the beam balance test and 2) the contractile parameters assessed in vitro of two skeletal muscles involved in the locomotion: a typical slow-oxidative muscle, the soleus, and a typical fast-glycolytic muscle, the extensor digitorum longus
The present study examined the effect of prolonged dietary exposure of two doses of CPF 1 mg kg−1 and 5 mg kg−1 in adolescent rats for 6 weeks on the locomotor activity and the physiological parameters of two types of skeletal muscles, a fast twitch skeletal muscle, edl and a slow twitch skeletal muscle, soleus, involved in the locomotion

Summary

Introduction

Even though lots of governmental regulations are being taken to limit the market growth of chlorpyrifos (CPF) over the coming years (up to 2022), it remains one of the most common organophosphorus pesticides used worldwide. This forecasted market growth can be referred to its increasing demand in various sectors, low cost and convenience [1]. According to the US Environmental Protection Agency (EPA), CPF is moderately persistent It may bioconcentrate at very low levels in ecological systems and can be detected in air, food and water. While the first two routes are more of a big concern in the occupational settings, the latter route poses an increase in health risk for the general population through eating food and drinking water contaminated with pesticides residues

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