Ultrastructural alterations in the kidneys of Pekin ducks fed methylmercury

Ultrastructural alterations in the kidneys of Pekin ducks were studied after subchronic exposure to methylmercury chloride. Twenty-four male and twenty-four female Pekin ducks, 12 weeks of age were fed 0.0 (control), 0.5, 5.0 and 15.0 parts per million of MeHgCl, mixed in a mash diet for 12 weeks. Birds were observed for clinical signs daily. Kidneys were fixed in situ by perfusion with 4% glutaraldehyde in 0.05 M phosphate buffer and routinely processed for electron microscopy. Only minor morphological changes were observed in the renal corpuscle of ducks in the 0.5 ppm group. The component cells of the renal corpuscle in the 5.0 and 15.0 ppm groups showed several ultrastructural alterations, including an increase in number and size of lysosomes and vacuoles in podocytes and mild vacuolation in mesangial cells. The juxtaglomerular cells of afferent arterioles had crystallized granules. No significant changes were observed in glomerular basement membrane thickness and width of podocyte pedicels. The proximal tubules of the 5.0 and 15.0 ppm groups showed some microvillar loss and an increase in the number and size of lipid droplets, vacuoles and lysosomal bodies. The distal tubular changes in the 5.0 and 15 ppm groups included electron lucency and vacuolation of cytoplasm as well as occasional mitochondrial swelling. The collecting ducts of 5.0 ppm and 15.0 ppm groups showed varying degrees of degenerative changes in both mucus secretory as well as absorptive cells. These results suggest that subchronic exposure of Pekin ducks to methylmercury chloride causes subtle ultrastructural changes in renal corpuscle and marked ultrastructural changes in proximal tubules and collecting ducts.