Effects of salt acclimation on water and urea permeabilities across the frog bladder: relationship with intramembrane particle aggregates

1. In salt-acclimated frogs, water and urea bladder permeabilities are markedly higher than in tap water-acclimated animals. 2. Intra-membrane particle aggregates (IMPA) cover an unusually large surface area of the salt-acclimated frog bladder apical plasma membrane. 3. In saline-adapted animals, proteins extracted from the apical plasma membrane contain additional species of 19, 26, 31 and 53-61 kDa. These proteins might be related to the water channels contained by IMPA.