Chloride conductance and mitochondria-rich cell density in isolated skin of Rana catesbeiana acclimated to various environments

Abstract

The Cl − conductance in isolated skin of frogs ( Rana catesbeiana) acclimated to 30 mM solutions of NaCl, Na 2SO 4, MgCl 2 and distilled water (DW) was studied. Transepithelial potential difference ( PD trans), short-circuit current ( I SC) and total conductance ( G t) were measured under conditions such that there was Cl − flux in the presence and absence of Na + transport. The Cl − content of the mucosal solution was acutely replaced with SO 4 2− or gluconate to evaluate the effect of removal of Cl − conductance on electrophysiological parameters. Mitochondria-rich cell density ( D MRC) was also measured. Skins from frogs acclimated to NaCl and Na 2SO 4 showed the lowest and the highest D MRC, respectively, but no difference could be found between the skins from frogs acclimated to DW and MgCl 2 indicating that D MRC is not unconditionally dependent on environmental Cl − in this species. Frogs acclimated to NaCl showed marked differences when compared to the other groups: the highest G t, probably represented by a higher paracellular conductance; the lowest transepithelial electrical potential difference which remained invariant after replacement of mucosal Cl − with SO 4 2− or replacement of mucosal Cl − with gluconate and an inwardly oriented positive current in the absence of bilateral Na +.