Larval bullfrog skin lacks amiloride-blockable epithelial transport because α-ENaC is located within intracellular vesicles in epidermal apical cells and not in the apical plasma membrane.
The epithelial Na channel (ENaC) plays an essential role in sodium transport across epithelia such as adult frog skin. Transport across the skin, measured as short-circuit current (SCC), is blocked by amiloride. Bullfrog alpha-ENaC (α-fENaC) is expressed in adult bullfrog skin, and the SCC across this skin is blocked by amiloride. In contrast, an amiloride-blockable SCC is not detected in larval bullfrog skin, even though it expresses α-fENaC. We examined the subcellular localization of α-ENaC in such larval and adult skins. Immunofluorescent and immunoelectron microscopy of apical cells in the larval epidermis revealed α-fENaC localization within intracellular vesicles, but not in the plasma membrane. In contrast, in adult skin α-fENaC was localized to the apical-side membrane and to intracellular vesicles in Stratum granulosum cells. This may support the view that amiloride-blockable SCC is absent from larval skin, but is present in adult skin.
Department of Physiology, School of Medicine, Saitama Medical University, Moroyama, Iruma-gunn, Saitama 3500495, Japan.
Kayo
K
Fujimaki-Aoba
Shinji
S
Komazaki
Philip J
PJ
Jensik
Shigeru
S
Hokari
Makoto
M
Takada
D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D022162:Cytoplasmic Vesicles / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D053503:Epithelial Sodium Channels / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D007814:Larva; D011892:Rana catesbeiana / Q000378:metabolism*; D012867:Skin / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure
D053503:Epithelial Sodium Channels; D000584:Amiloride