Development of the embryonic murine kidney in normal and congenital polycystic kidney disease: characterization of a proximal tubular degenerative process as the first observable light microscopic defect.

The current report presents findings from a comparative histological and histochemical investigation of murine congenital polycystic kidney disease. The studies revealed that the morphological changes are initiated in the developing proximal tubules of the nephron; differences from control sections first become evident at 16 days' gestation. As the disease progresses, obvious changes include hyperplasia and dilation of the tubule, cellular vacuolization, and alterations in the apical cell brush border. Included among the latter changes are decreases in enzyme (alkaline phosphatase) staining and decreases in glycoprotein staining (periodic acid Schiff). All such changes continue until the kidney is markedly cystic and apical cell cytochemical staining is absent. Some cellular vacuolization, assumed to be a normal developmental event, is also seen within the same segment of the proximal tubule at 17 days' gestation through the 1st postnatal day. Dilation of the collecting duct is noted to be a later or secondary change evident after the initial onset of the disease.