Hyperplastic changes in the rat distal tubular epithelial cells following in utero exposure to methylmercury

Female Sprague—Dawley rats were injected with 1.0 mg methylmercury chloride on the eighth day of pregnancy. Tissues from the renal cortex of the offsprings were sampled for electron microscopy. Besides degenerative changes in the proximal convoluted tubules, hyperplastic changes were observed in the distal convoluted tubules. Increased mitotic index was found in many distal tubular epithelial cells. Hyperplastic thickening of these tubular linings was also observed. Such hyperplastic changes may be suggestive of premalignant changes.