Studies On Iron Metabolism Of Megalobrama Amblycephala Challenged By Aeromonas Hydrophila

Iron is essential to almost all organisms and most of the pathogenic bacteria. A competition developed between the pathogenic bacteria and its host because of the common demand to iron. Blunt snout bream(Megalobrama amblycephala) has been regarded as a principal species in Chinese fresh-water culture systems. However, disease caused by Aeromonas hydrophila severely hinders the healthy and sustainable development of blunt snout bream cultivation. In order to reveal the pathologic changes and study the influence of A. hydrophila infected on iron metabolism in blunt snout bream, a total of 480 fish(30±5 g) were randomly divided into experimental group and control group. The pathology, level of iron metabolism and expression of related genes in blunt snout bream challenged by A. hydrophila were tested. The research results were summarized as follows: 1. The pathologic changes of blunt snout bream challenged by A. hydrophilaThe onset of the lesions began to appear at 4 to 12 h post-challenge. Liver cells revealed structural disorders with vacuolar degeneration, edematous and the cell nucleus skewing under the microscope. The cell boundary of liver cells was unclear. A lot of blood cells infiltrated into liver tissue. Compared with the health spleen, the diseased spleen cells showed swollen, vacuolated, obvious hemorrhage and disorganized structures. The pathologic degrees of kidney tubules were disparity. Some cells in kidney became vacuoles. Swollen and structure disturbance emerged in some epithelial cells of renal tubule. The glomerulus capillary dilated and seriously rarefaction and vacuoles of the renal corpuscle structure could be seen. The submucosa and serosa cells arranged loosely with thickening, swollen. The muscle fibers arranged disordered with voids. There were a lot of blood cells infiltrated into submucosa, serosa and muscular layer. The intestinal villi fell away and the ciliated columned epithelium cells emerged degeneration, dropped and the number of goblet cells was enhanced. 2. The influence of A. hydrophila infection on iron metabolism of M. amblycephalaCompared with the control group serum, iron concentration at various time points in the experimental group decreased differently and reached a significant level at 12 h and 24 h after challenged(P<0.05). Compared with the control group, Serum total iron binding capacity of the experimental group increased slightly, but did not reach significant levels. The results of iron staining and iron content in the liver showed that compared with control group the iron content in the liver of experimental group was higher, but did not reach significant levels(P>0.05). 3. Expression of iron metabolism-related genes in blunt snout bream challenged by A. hydrophilaCompared with health blunt snout bream, the expression of hepc gene in liver increased significantly(P<0.05) at various time points after challenge and reached extremely significant level at 4 h and 12 h post-challenge(P<0.01). The expression of il-6 gene in the liver increased significantly at 4 h and 12 h post challenge(P<0.05), which reached extremely significant level at 24 h(P<0.01). Jak3 gene expression increased significantly in liver at 4 h and 12 h post challenge(P<0.05), and then declined slightly. Stat3 gene expression increased extremely significantly at 4 h, 12 h and 24 h post challenge(P<0.01), and then declined slightly, which reached significant level at 72 h post-challenge(P<0.05). The expression of bmp6 gene reached extremely significant level at 4 h, 12 h post challenge(P<0.01), significant level at 24 h post-challenge(P<0.05), and then declined. The expression of bmprⅡb gene increased significantly(P<0.05) at various time points after challenge and reached extremely significant level at 24 h(P<0.01). Hfe2 gene expression increased significantly at 72 h and 120 h(P<0.05) and reached extremely significant level at 12 h and 24 h post challenge(P<0.01). The expressions of smad5 gene and smad4 gene increased significantly(P<0.05) at various time points after challenged(P<0.05).