Protective action of astragalus polysaccharides on kidney in diabetic rats

Abstract

Aim: To probe into the mechanism of the therapeutic effect of astragalus polysaccharides (APS) against diabetes mellitus rats by measuring renal medullary aquaporin-2 (AQP-2), the change of urinary volume in 24 hs, as well as observing kindey ultramicroscopic structures. Methods: Thirty diabetes mellitus (DM) rats induced by streptozotocin (STZ) were randomly divided into three groups: DM group, APS 200 mg·kg-1·d-1 group, and APS high dosage group. Another 10 normal rats were taken as the control group. The drug was given by introperitonial injection for 6 weeks. A 24 h urine collection through simple metabolic cage was made to measure urinary volume; the RT-PCR technique was used to determine the levels of AQP-2 mRNA expression in kidney medulla. Kidney medulla ultramicroscopic structures were observed by TEM. Results: Diabetic rats showed a significant increase in urinary volume compared with control rats. The urine amount of low and high dosage APS treatment could obviously increase the urinary volume (P < 0.05); the expression of AQP-2 mRNA was up-regulated in the kidney of diabetic rats. Low and high dosage APS treatment could alleviate the over expression of AQP-2 mRNA (P < 0.05). It showed degenerative changes of distal tubule and collecting tubes chief cells ultramicroscopic structures of the DM, APS low dose and high dose treatment group in contrast with the control group, while APS Long-term treatment could significantly improved the damage. Conclusion: APS exerts its therapeutic effects on diabetes mellitus, which may be related to the significantly decreased expression of AQP-2 mRNA in the kidney medullary.