Abstract: Objective To explore the effect of slit guidance ligand 3（Slit3）on rats with diabetic kidney disease（DKD）-induced fibrosis. Methods A DKD rat model was established by multiple lowdose injections of streptozotocin combined with high-sugar high-fat diet. Forty Sprague-Dawley（SD） rats were randomly divided into the blank control group（control），diabetes mellitus（DM）group，4- week DKD group and 8-week DKD group，with 10 rats in each group by random number table method. After successful modeling，there were 8 rats in the control group，and 6 in each of the remaining groups. The 24 h urinary protein content was detected. Total cholesterol（TC），triglyceride（TG），blood urea nitrogen（BUN），serum creatinine（Scr），and albumin（Alb）were analyzed after abdominal aorta blood collection. Hematoxylin and eosin（H&E）staining was used to observe the histopathological changes of the kidney. Kidney fibrosis degree was examined by Masson’s trichrome staining. The reversetranscription quantitative real-time polymerase chain reaction （RT-qPCR） was performed to detect mRNA levels of Slit3，α-smooth muscle actin（α-SMA），and transforming growth factor-β1（TGF-β1） in kidney tissues，and their protein levels were detected by Western blot. The expression and localization of Slit3 in kidney tissues were detected by immunohistochemical staining. Results Compared with the control group，24-hour urinary protein content［（37. 18 ±5. 55）mg、（47. 38 ±18. 19）mg vs（10. 66 ±4. 87）mg］，BUN［（19. 18 ±7. 97）mmol/L、（21. 01 ±6. 74）mmol/L vs（6. 86 ±1. 15）mmol/L］and Scr［（58. 02 ±12. 49）μmol/L、（61. 18 ±20. 76）μmol/L vs（28. 34 ±3. 35）μmol/L］of 4-week and 8- week DKD groups were significantly higher（P<0. 05）. In comparison to the control group，TC［（3. 75 ±3. 21）mmol/L、（2. 44 ±2. 08）mmol/L vs（1. 37 ±0. 32）mmol/L］was significantly higher，while TG ［（0. 46 ±0. 64）mmol/L、（0. 32 ±0. 50）mmol/L vs（0. 93 ±0. 46）mmol/L］was significantly lower in the 4-week and 8-week DKD groups（P<0. 05）. Compared with the control group，the protein levels of Slit3［（0. 100 ±0. 002）、（0. 120 ±0. 003）vs（0. 050 ±0. 006）］，α-SMA［（0. 370 ±0. 011）、（0. 590 ±0. 003）vs（0. 070 ±0. 006）］and TGF-β1［（0. 810 ±0. 024）、（0. 940 ±0. 01）vs（0. 520 ±0. 028）］in rat kidney tissue were significantly higher in the 4-week and 8-week DKD groups（P<0. 05）；so as their mRNA levels［（2. 520 ±0. 164）、（3. 016 ±0. 226）vs（1. 020 ±0. 034）；（3. 010 ±0. 160）、 （3. 560 ±0. 218）vs（1. 000 ±0. 100）；（3. 030 ±0. 185）、（3. 550 ±0. 194）vs（1. 010 ±0. 087）］. Compared with the DM group，the protein levels of Slit3［（0. 100 ±0. 002）、（0. 120 ±0. 003）vs （0. 070 ±0. 004）］，α-SMA［（0. 370 ±0. 011）、（0. 590 ±0. 003）vs（0. 220 ±0. 014）］and TGF-β1 ［（0. 810 ±0. 024）、（0. 940 ±0. 010）vs（0. 700 ±0. 028）］in rat kidney tissue were significantly higher in the 4-week and 8-week DKD groups（P<0. 05），especially in the 8-week DKD group（P<0. 01）. No significant differences in the mRNA levels of Slit3，α-SMA and TGF- β1 were examined in the rat kidney tissue between 4-week and 8-week DKD groups（P>0. 05）. Conclusion Slit3 can significantly aggravate kidney fibrosis in DKD rats.