Effects of environmental conditions on mitochondrial-rich cell density and chloride transport in toad skin.
Chloride flux across amphibian skin is usually passive, yet largely conductive; previous reports have suggested that aldosterone influences this pathway. The conductive Cl- pathway and its regulation were examined further, across the abdominal skin of toads (Bufo marinus) adapted to various environments. Short-circuit current (Isc), total conductance (Gt) and Cl- influx (JCl) were measured in conditions such that there was net Cl- movement in absence of Na+ transport. In salt-deprived animals compared to salt-adapted ones, there was a significant increase in JCl (563 vs 200 pmol cm-2 s-1), aldosteronaemia (4.2 vs 1.1 nmol/l), as well as MRC density (1458 vs 851 mm-2). After adaptation to dilute Na2SO4 compared to MgCl2, JCl (631 vs 313 pmol cm-2 s-1) as well as the density of mitochondria-rich cells (MRC) (1306 vs 710 mm-2) practically doubled, while the toads' aldosteronaemia was lower (2.4 vs 10.8 mmol/l). In all groups of toads, JCl was matched by Isc, and there was a close correlation between Gt and JCl (r = 0.96), which confirms the conductive nature of transepithelial Cl- movement. Furthermore, the relationship between JCl and MRC density (r = 0.75) argues in favour of a role played by MRC on Cl- conductance of epithelial such as amphibian skin. As aldosterone injected for 1 week into NaCl-adapted toads did not influence MRC density and as aldosteronaemia was not correlated with Cl- conductance, this hormone does not emerge as the determinant of these parameters.
Devuyst
O
O
Department of Physiology, U.C.L. Medical School, Brussels, Belgium.
Beaujean
V
V
Crabbé
J
J
D000450:Aldosterone / Q000502:physiology; D000818:Animals; D001692:Biological Transport; D002024:Bufo marinus / Q000502:physiology*; D002452:Cell Count; D002455:Cell Division; D002462:Cell Membrane / Q000502:physiology; D002463:Cell Membrane Permeability / Q000502:physiology; D002712:Chlorides / Q000493:pharmacokinetics*; D004553:Electric Conductivity / Q000502:physiology; D004777:Environment; D008564:Membrane Potentials; D008928:Mitochondria / Q000648:ultrastructure*; D012867:Skin / Q000378:metabolism / Q000648:ultrastructure; D012879:Skin Physiological Phenomena; D012964:Sodium / Q000493:pharmacokinetics / Q000502:physiology
D002712:Chlorides; D000450:Aldosterone; D012964:Sodium