Effects Of Astragalus Polysaccharides On Relieving Transport Stress-induced Cardiac Ionic Disorders In Neonatal Chicks

The first transportation stress of the chicken occurs as soon as they hatched,which are transported from the hatchery to the breeding farm.This process is harmful to the physiological functions and production performance of the chickens.As an important organ of the circulatory system,heart is one of the most target organs for transport stress,and ionic disorders during stress and may also be one of the mechanisms of transport stress injury.Astragalus polysaccharides（APS）is one of the main extracts of Astragalus membranaceus.It plays an important role in protecting organisms against stress.However,the effect and mechanism of APS in protecting heart against transport stress-induced cardiac ion disorders is not clear.In order to reveal the effect and mechanism of APS in protecting heart against transport-induced cardiac ion disorders,untransportable neonatal chicks were employed in this study.Shaking tables were used to simulate transport stress and APS was given to the chicks by oral administration.Body weight and cardiac pathological alterations were observed,and related indicators were detected including cardiac function index,expression level of ATPase-related subunit gene,enzyme activity,and serum and tissue ion content.The results indicated that:1.The transport stress can lead to the weight loss of the neonatal chicks and the myocardial cell edema,and the activity of myocardial enzymes is increased.APS can reduce the transport stress-induced weight loss of neonatal chickens,protect heart function,alleviate myocardial cell edema,and relieve the cardiac stress injury.2.At the early stage of transport stress（2h,4h）,the organism up-regulates ATPase activity,increased inflow of Mg²⁺and Cl^-ions into the cardiomyocytes to resist transport stress with the extension of transport time,and the enzyme activity was inhibited and the ions appear disordered;whereas APS upregulates the mRNA expression level of cardiac NKA,Ca²⁺-ATPase related subunits,and increases the activity of NKA enzyme to regulate the ion concentration in cardiomyocytes and serum against transport stress-induced myocardial cell disorders.Meanwhile,the antagonistic effect to long-term transport（8h）was more significant.3.Short-term transport stress（<4h）can up-regulate cardiac ion channel NKA,Ca²⁺-ATPase and Mg²⁺-ATPase activities.Long-term transport stress（>8h）can down-regulate ion channel ATPase activities,and significantly down-regulate the expression of cardiac ion channel ATPase-related subunit genes,and leading to the disordered ion channel ATPase function.Whereas APS can regulate cardiac ATPase activities and up-regulates the expression of ATPase related subunits,and ameliorate the disorders of cardiac ion channels caused by transport stress,suggesting that the amelioration of ion channel regulation disorders is one of the mechanisms by which APS ameliorates ion imbalance in transporting stress-induced ion homeostasis.In conclusion,transport stress can cause heart damage in newborn chicks.APS can ameliorate imbalance of ion homeostasis and improve ion channel ATPase enzyme regulation disorders by alleviating cardiomyocyte edema,which is an important mechanism where APS exerts its role in mitigating transport stress-induced heart damage in chicks.