Effect Of Zinc Deficiency On Zn～(2+) And ZnT7 Expression In Mouse Superior Cervical Ganglion

Zinc is a necessary trace element and spreads all over the organs in human body. It has been approved that zinc is important for growth and immunity, and for the development of the nervous system. Several studies have shown that Zn exists in both the central nervous system ( CNS) and the peripheral nervous system ( PNS) . However, the function of Zn²⁺ in the nervous system, especially in the PNS is not very clear so far. Some investigators presumed that Zn²⁺ might play roles in some adrenergic nervous system.The accumulation and transmembrane transport of Zn²⁺ in mammalian cells are related to a zinc transporter (ZnT) family, which contains seven members, i. e. ZnT1 — ZnT7. The aim of this study is to study the effect of zinc deficiency on Zn²⁺ and ZnT7 expression in mouse superior cervical ganglia (SCGs) by u-sing autometallography (AMG) and immunohistochemistry. This study will provide a morphological basis for further understanding the functional roles of Zn and ZnT7 in the PNS.Materials and MethodsThree — week — old mice were divided into two groups, zinc deficiency (ZnD) group and normal group. They were given ZnD food and normal food, respectively. Five weeks later, the expression of Zn²⁺ and ZnT7 were detected by using AMG and immunohistochemistry. The localizations of Zn²⁺ in mouse SCGs were examined at both light and electron microscopic levels. The image a-nalysis system was used to evaluate the average optical density of positive reactive granules and the proportion of positive reactive cells in the postganglionic neurons in the SCGs. The above data between normal and ZnD groups were examined by using t - test.ResultsNearly 55% of total postganglionic sympathetic neurons in mouse SCGs of normal group showed AMG positive reactivity and nearly 50% neurons showed ZnT7 positive reaction. In ZnD group, AMG positive and ZnT7 positive neurons were about 36% and 30% of total neuronal numbers in SCGs, respectively. Significant deviation could be seen between the two groups.With the time of sodium selenite injection passed, the expression of Zn + in SCGs decreased obviously. Seventy - two hours after selenite injection, only 3% neuron in SCGs expressed the Zn2+ positive reaction. At electron microscopic levels, zinc ions were located in the Golgi apparatus and vesicles around the nuclear in mouse SCG neurons.Conclusion1. Expression of Zn + and ZnT7 could be observed in mouse SCG. The positive reactive products reduced in ZnD group.2. The location of Zn2 + in Golgi apparatus and vesicles suggested that Zn2 + may be involved in proteins synthesis and packaging. ZnD may lead to the dys-synthesis of these proteins.3. ZnT7 may be involved in the transport of Zn + in SCG. Zn + and ZnT7 could be presumed to play functional roles in sympathetic nervous system.