| The ostrich has huge economic and the precious scientific research values. The ostrich industry is now growing and developing, and ostrich has been widely cultured in the world. Inorganic boron takes part in many various life metabolic activities, which is related to the body growth and immune system. Additionally, a large number of scientific researchers reported that low-dose boron has nutritional and promotive effects on the body, thus boron is a necessary trace element for animals and but high-dose boron has inhibitory effect. In addition, the boron also plays an extraordinary role in regulating the process of antioxidant system and cell apoptosis, which indirectly affect animals’ organizational structure. The boron absorbed is ultimately eliminated as original form by kidney. But the development of each organ of ostrich chicks is still not well, so ostrich chicks has low resistance and are vulnerable to be damage by external factors. As a result, to investigate the effect of boron supplementation in water on the antioxidant system and Nrf2 mediated oxidative stress pathway in the ostrich chick kidney, the study supplemented the boron,which was in the form of boric acid, in the water at the concentration of 0 mg/L,40 mg/L,80 mg/L, 160 mg/L, 320 mg/L and 640 mg/L, respectively. In each group the paraffin sections of kidney tissues of 90-day-old ostrich chicks have been made at the end of the research. And for investigating the effects of different levels of boron administration in drinking water on the ostrich chick’s kidney tissue, the technique such as HE, immunohistochemistry and TUNEL,MDA,GSH-PX and T-AOC assay and quantitative real-time PCR were been used. The corresponding contents and results in the research are as follows:1 The effect of boron supplementation on morphological structure of ostrich kidneyMicroscopic observation showed that compared with the control group(0 mg/L),the structure of renal corpuscle and renal tubular was clearer and the epithelial cells were in good arrangement in the boron supplemented groups of 40 and 80 mg/L. Furthermore, the brush borders were more abundant; no obvious morphological changes were observed, except slight expansion of glomerular capillary and steatosis in few renal tubular epithelial cells in the 160 mg/L boron group; On the other hand,histopathological degeneration occurred with the characters of cellular swelling and dissociation,loose cytoplasm,nuclear pycnosis,and basement membrane detachment in some tubular cells. Debris deposit was accumulated in the tubular lumen, especially in the proximal tubule in groups fed with 320 and 640 mg/L boron.2 The effects of boron on apoptosis of on ostrich chicks kidney tissueIt is known that HE stained observed in 160,320 and 640 mg/L Groups,cellular swelling and dissociation, nuclear pycnosis and loose cytoplasm in proximal tubular cells, suggesting that 160-640 mg/L boron might increase cell apoptosis in kidney tissue. To confirm this conclusion, TUNEL was used. The results found that compared with the control group, the apoptosis cells distributed balance in all places but the number of apoptosis cells were significantly reduced in the 40 and 80 mg/L boron groups, suggesting that 40 and 80 mg/L boron could inhibit apoptosis significantly; Moreover, the number of apoptosis cells in 160 mg/L boron group has a slight increase;whereas when the dose of boron was up to the 320 and 640 mg/L,the number of apoptosis cells were significantly increased, and 640 mg/L boron group reached the peak with the apoptosis cells be mainly distributed in renal proximal tubules, suggesting that 320 and 640 mg/L boron concentration would promote cell apoptosis.3 The effects of boron on antioxidant capacity in ostrich chicks’ kidney tissueMDA, GSH-PX and T-AOC assay were used for the assessment of the effects of boron on antioxidant capacity. The results revealed that compared with control group,the GSH-PX and T-AOC activities in 40 and 80 mg/L boron were significantly increased,but MDA content were significantly reduced,suggesting that concentration of boron at 40 and 80 mg/L, especially 80 mg/L, could improve the ostrich chicks kidney tissue antioxidant capacity; However, MDA content at 160-640 mg/L boron showed an significant increasing trend, especially at the concentration of 640 mg/L,meanwhile the T-AOC activity were significantly declined, suggesting that high levels of boron could enhance the lipid peroxidation and content, and may damage the body’s antioxidant capacity.4 The effects of boron on Nrf2 pathway in ostrich chicks kidney tissueNrf2 pathway is a most important way in antioxidant capacity and regulates the cell’s redox homeostasis control program. In addition, Nrf2 pathway also can inhibit cell apoptosis. The expression of three important gene in Nrf2-mediated antioxidant response(Nrf2、HO-1 and GCLc) were measured by quantitative real-time PCR. The results indicated that proper amount of boron addition(especially 80 mg/L) significantly increased the gene expression levels, suggesting 80 mg/L boron enhanced the baseline antioxidant capacity;with increasing dosage of boron,the gene expression levels in 320 mg/L and 640 mg/L were also shown to be significantly increased in the high boron groups, but lower than 80 mg/L group, demonstrating up-regulating the expression of Nrf2、HO-1 and GCLc could reduce the oxidative damage and cell apoptosis due to high boron, however, the increase was gradual.5 The effects of boron on localization and expression of Nrf2 in ostrich kidneyNrf2 serves as a vital mediator in the cellular defense against oxidative stress,therefore the study was to investigate the on localization and expression of Nrf2 in the ostrich chick kidney using immunohistochemical technology. The results showed that Nrf2 was mainly distributed the expression level was significantly higher than the control group. The groups fed with boron concentration from 160 to 640 mg/L also could increase the Nrf2 expression,but the distribution of Nrf2 sandy particles was in the majority with state of aggregation compared with the control group.In conclusion, the low levels of boron(40 and 80 mg/L,especially 80 mg/L) improve ostrich chicks’ kidney tissue antioxidant capacity, inhibit the cell apoptosis significantly,and thus may improve the ostrich chick’s kidney tissue development;high levels of boron(320 and 640 mg/L, especially 640 mg/L) would enhance the lipid peroxidation, reduce the antioxidant capacity, promote cell apoptosis, and thus damage the ostrich chicks kidney tissue morphological structure, which was mainly via the Nrf2 pathway. |
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