Effects of an external charged layer on transepithelial ion movement in frog skin

Responses of skin mucous cells to aluminium exposure at low pH in Atlantic salmon (Salmo salar) smolts

“…A function of mucus in prevention of an osmotic dis turbance by Al exposure, e.g., by forming a diffusion barrier to passive plasma ion movement across the skin and gill mem brane or to concentrated cations near the epithelial surface to aid the active uptake of ions, seems to be unlikely because Na+,C1", and Ca2+ diffusion is not substantially affected by mucus layers, as measured on dilute solutions of mucus (Marshall 1978;Part and Lock 1983;Stith 1984). More likely, mucus has an indirect function by retarding Al diffusion from the solution to the membrane surface, thus reducing the negative impact of Al on the epidermal surface (Wilkinson and Campbell 1993).…”

Physiological and morphological correlates of extreme acid tolerance in larvae of the acidophilic amphibianLitoria cooloolensis

“…Mucus has several well established roles including the development of an unstirred layer and facilitation of ion/water transport (Handy et al, 1989; Shephard, 1981; Shephard, 1982), as an immunological barrier (Swidsinski et al, 2007) and in the control of gas exchange across epithelia (Wright et al, 1989). Mucus production is often stimulated by noxious substances such as low pH (Bohmer and Rahmann, 1990; Leino and Mccormick, 1984; Linnenbach et al, 1987; Walker et al, 1988), where its primary function is likely increasing the distance between the cell surface and the environment (Henriksnas et al, 2006; Phillipson et al, 2008) and neutralising hydrogen ions before they reach the apical surface of epithelial cells (Holma, 1985; Phillipson et al, 2008; Stith, 1984a; Stith, 1984b). Other studies have demonstrated an important role for branchial mucus in concentrating electrolytes within an unstirred layer, thereby preventing ion leak from epithelia (Handy et al, 1989) and also promoting Na + uptake (Stith, 1984a; Stith, 1984b).…”

“…Mucus production is often stimulated by noxious substances such as low pH (Bohmer and Rahmann, 1990; Leino and Mccormick, 1984; Linnenbach et al, 1987; Walker et al, 1988), where its primary function is likely increasing the distance between the cell surface and the environment (Henriksnas et al, 2006; Phillipson et al, 2008) and neutralising hydrogen ions before they reach the apical surface of epithelial cells (Holma, 1985; Phillipson et al, 2008; Stith, 1984a; Stith, 1984b). Other studies have demonstrated an important role for branchial mucus in concentrating electrolytes within an unstirred layer, thereby preventing ion leak from epithelia (Handy et al, 1989) and also promoting Na + uptake (Stith, 1984a; Stith, 1984b). The diffusion of low-charge ions, like monovalent electrolytes, through the mucosal unstirred layer is many cases similar to that through normal saline indicating that mucus is not a major obstruction to the effective uptake of these ions (Handy and Maunder, 2010).…”