Scanning electron microscopy of the juxtaglomerular apparatus in the freeze-fractured rat kidney.

The morphology of the juxtaglomerular apparatus of the rat kidney was investigated by scanning electron microscopy of the freeze-fractured tissue. The macula densa cells have a dome-shaped apical surface abundantly provided with short microvilli. Their basal and lateral aspects may show labyrinthine spaces which are consistently more developed than in the epithelium across the tubular lumen. The Goormaghtigh cells display the well known complex pattern of cytoplasmic extensions forming the lacis. Fractured juxtaglomerular cells show distinct nuclei and well defined secretory granules. The well developed labyrinth of the macula densa suggest a considerable trans-epithelial fluid transfer at this level.