Zinc disc implantation model of urinary bladder calculi and humane endpoints

The zinc disc implantation-induced urinary bladder calculi model in the rat is commonly used for preclinical evaluation of the antiurolithiatic activity of test compounds. Certain published reports state that relatively long durations for which zinc discs must be implanted in the bladders of rats. Hence, there is a need to refine this model. These investigations aimed to determine whether long-term studies using the zinc disc implantation model provide any additional data that affect the final outcomes of the study. In this study, we evaluated the effects of a well-known antiurolithiatic polyherbal drug, Cystone, for different treatment durations of 10, 20 and 48 days postimplantation. Our results indicate that even the shortest duration of 10 days is sufficient to reveal antiurolithiatic effects of a test drug. Hence, in the zinc disc implantation-induced urinary bladder calculi model, the study duration is proposed to be minimized so as to reduce the distress caused to the rats due to long-term exposure to the implant. Further, it is suggested that the growth of the bladder calculi can be monitored by taking X-ray radiographs of the bladder deposits to decide the time to terminate the study. Use of preformed calcium oxalate crystal instead of zinc discs, as suggested in earlier reports by others, may also be considered to avoid the sacrifice of rats at the end of the study.