The Studies On The Mechanism Of Sub-Chronic Manganism To The Nervous System Of Cock

Manganese is a essential trace element for organisms and plays an important role in growth, development and breeding. However, excessive manganese disturbs nervous, immune, respiratory and cardiovascular systems and results in manganis. Brain is the main target organ of manganism. In recent years, reaserches on manganism are increased, but most of the reaserch activity mainly focused on human and mouse tissues, reports about poultry are very few.In the study, 100 Hyline cocks of 50 days old were used to be respectively fed a diet with Manganese 600 mg/kg, 900 mg/kg and 1800 mg/kg for 30 d, 60 d and 90 d. Clinical symptoms, postmortem, microstructure and ultrastructure were observed and contents of Mn, Fe, Cu, Zn, Ca and Se in cerebrum, activity of NO and NOS in serum and cerebrum, restraining ability to·OH and activity of SDH, ATPase and CaN, the content of [Ca²⁺]_i, apoptosis and expression of CaN, CaM and iNOS mRNA in nerve cell were measured to assess the effect of manganism on cerebrum function of cocks and clarify preliminary toxicity mechanism of manganism to cerebrum. The results showed as follows:1. By the detection of the contents of Mn, Fe, Cu, Zn, Ca and Se, it was revealed that manganese could cumulate in central nervous system, and cause the unbalance of trace element. These results indicated that manganese could cause central nervous system injury.2. The changes of the content of NO, the activity of NOS and restraining ability to·OH as well as the expression of iNOS mRNA, revealed that excessoive manganese decreased the content of NO,which mediated the damage of nerve cell. This might be one of the mechanisms of nervous system injury caoused by manganism.3. Based on the detection of SDH content and [Ca²⁺]_i content, the activity of ATPase and CaN, and the expression of CaM and CaN, the results revealed that excessive manganese could inhibitive enzyme activity of tricarboxylic acid cycle, lead to energy metabolic disturbance, decrease the activity of ATPase, and cause the disorder of extra and intracellular dynamic equilibrium and high concentration of calcium.These results revealed that excessive manganese could cause energy metabolic disturbance and high concentration of calcium. This may be one of the manganese neurotoxicity mechanism.4. Manganism led to apoptosis happened in cerebrum from the evidence of ultrastructural changes of apoptosis and the result of Tunel, which indicated that manganism induce neuronal apoptosis and damage the central nervous system. It was concluded that sub-chronic manganism can destructe the balance of elements in the brain, generate large amout of NO, interfere the energy metabolism of mitochondrion, initiate the imbalance of calcium homeostasis, induce apoptosis, damage the central nervous system, which maybe involved in the mechanism of manganism.