A scanning electron microscopic study of the cytoplasmic surface of the toad bladder luminal membrane

Antidiuretic hormone (ADH) increases water flow across receptor cells in the kidney and amphibian bladder by stimulating the insertion of particles into the luminal (urinary) cell membrane. The particles originate from tubular structures in the cytoplasm which fuse with the luminal membrane. Many of the steps involved in fusion and particle insertion are still unknown. We have been able to separate the luminal cell membrane of ADH-treated toad bladder from the rest of the cell and attach the membranes to glass coverslips with polylysine, with their cytoplasmic surfaces facing up. Inspection of the membranes by scanning electron microscopy reveals subluminal granules and what appear to be fusing tubules. The present communication describes our technique for membrane preparation and adhesion, as well as our initial observations of membrane-associated organelles.