ADH and phorbol ester increase immunolabeling of the toad bladder apical membrane by antibodies made to granules

Summary Polyclonal antibodies were raised to isolated toad bladder granules. On immunoblots, the anti-granule antiserum specifically stained components of isolated granules. Immunocytochemically, the anti-granule antiserum labeled the apical surface of the bladder. Immunolabeling increased at the apical surface when the bladder was exposed to antidiuretic hormone (ADH) serosally or phorbol ester (PMA) mucosally—conditions which stimulate apical granule exocytosis. The increase in granule epitopes on the apical surface was sixfold greater than the net increase in surface area.