Soy-deficient diet induces renal lesions in juvenile rats

Certified LabDiet^® 5K96 Advanced Protocol™ Verified Casein Diet 10 IF (5K96) is a commercial diet low in soy isoflavones developed for use in developmental and reproductive toxicity (DART) studies, especially those designed to detect endocrine disruptors. The objective of this study was to determine the incidences and severities of 5K96-associated renal lesions in control F₀ and F₁ cohorts of rats fed the 5K96 diet. Kidneys from control animals of four DART studies involving Sprague-Dawley rats fed the 5K96 diet, were evaluated microscopically. Mineralization and basophilic tubules were present in high incidence/severity in males and females compared to historical controls fed conventional diets. F₁ cohorts were affected to a far greater degree than F₀ cohorts, and females were affected more than males. Consideration of target tissue and mode of action should be given before automatically incorporating the 5K96 diet into DART study designs, and caution should be exercised when identifying and interpreting renal toxicity in the F₁ cohorts of such studies.