Study On Effects Of Manganism On The Damage Mechanism Of Cock's Heart

Manganese is essential trace element for organisms, which plays an important role in growth, development and breeding, but excessive manganese disturb nervous, immune, respiratory and cardiovascular systems and result in manganis. The researches about manganism mainly focus on nervous and immune systems, not on cardiovascular system especially involved in poultry. In the study, Hyline cocks 100 were used to be respectively fed a diet with Manganese chloride 100 mg/kg (control group),600 mg/kg (low dose group),900 mg/kg (moderate dose group) and 1800 mg/kg (high dose group) for 30 d, 60 d and 90 d. Clinical symptoms, postmortem, microstructure and ultrastructure were observed and electrocardiography, contents of Mn, Fe, Ca, Cu, Zn in cardiac muscle, activity of CK and cTnT in serum, activity of superoxide dismutase activities (SOD) and total antioxidative capacity (T-AOC), mitochondria membrane permeability transition (MMTP), activity of mitochondrial respiratory chain complex (MRCC)â… ,â…¡,â…£in mitochondria, apoptosis and expression of SERCA2a mRNA in cardiac muscle were measured to assess the effect of manganism on heart function of cocks and clarify preliminary toxicity mechanism of manganism to heart. The results showed as follows:1. Manganese accumulated in cardiac muscle of cocks undergoing manganism with incremental contents of Cu and decreasing contents of Fe. The contents of Zn didn't display visible change and the contents of Ca displayed irregrlar and fluctuant change.2. Heart rate and electrical axis of heart had no changes, but high-dose and long-term manganism may cause the decreasion of voltage of P,R,S,T by leadâ…¡, which indicated high-dose and long-term manganism disturbed the function of heart.3. Serum creatine kinase and cardiac troponin obviously increased with the rise of dose, which displayed the dose-effect dose-effect relationship and indicated the damage of cardiac muscle.4. The decreasing activities of Na⁺-K⁺-ATPase,Ca²⁺-ATPase,Mg²⁺-ATPase, ability of antioxygen as well as activity of MRCCâ… ,â…¡andâ…£decreased combined with the change of MMTP reflected the interference to energy metabolism of mitochondria from manganism.5. Manganism led to apoptosis happened in cardiac muscle cell from the evidence of ultrastructural changes of apoptosis and the result of Tunel, which indicated that manganism reduced effective cardiac muscle cells by apoptosis and inhibited the function of heart.6. Expression of SERCA2a mRNA in short term manganism decreased but in long term it recovered. The larger the dose is, the faster and larger the return is. The result showed the interference from manganism to transport of Ca²⁺ of cardiac muscle.It was concluded that manganism can interfere in energy metabolism of mitochondria, affect the ability of antioxygen, induce apoptosis and alter mRNA expression of SERCE2a, which maybe involved in the mechanism of manganism and lead to the influence on cardiac function of cock and the injure of heart muscle.