Ion transport mechanisms in the mesonephric collecting duct system of the toad Bufo bufo: microelectrode recordings from isolated and perfused tubules.

TY - JOUR

T1 - Ion transport mechanisms in the mesonephric collecting duct system of the toad Bufo bufo: microelectrode recordings from isolated and perfused tubules.

AU - Møbjerg, Nadja

AU - Larsen, Erik Hviid

AU - Novak, Ivana

N1 - Keywords: Animals; Bufo bufo; Cell Membrane; Chlorides; Electrophysiology; Embryo, Nonmammalian; Ion Transport; Isoproterenol; Kidney Tubules, Collecting; Mesonephros; Microelectrodes; Perfusion; Sodium; Vasotocin

PY - 2004

Y1 - 2004

N2 - It is not clear how and whether terrestrial amphibians handle NaCl transport in the distal nephron. Therefore, we studied ion transport in isolated perfused collecting tubules and ducts from toad, Bufo bufo, by means of microelectrodes. No qualitative difference in basolateral cell membrane potential (Vbl) was observed between tubules and ducts in response to ion substitutions, inhibitor and agonist applications. Cl- substitution experiments indicated a small Cl- conductance in the basolateral membrane. The apical membrane did not have a significant Cl- conductance. Luminal [Na+] steps and amiloride application showed a small apical Na+ conductance. Arginine vasotocin depolarized Vbl. The small apical Na+ conductance indicates that the collecting duct system contributes little to NaCl reabsorption when compared to aquatic amphibians. In contrast, Vbl rapidly depolarized upon lowering of [Na+] in the bath, demonstrating the presence of a Na+-coupled anion transporter. [HCO3-] steps revealed that this transporter is not a Na+-HCO3- cotransporter. Together, our results indicate that a major task of the collecting duct system in B. bufo is not conductive NaCl transport but rather K+ secretion, as shown by our previous studies. Moreover, our results indicate the presence of a novel basolateral Na+-coupled anion transporter, the identity of which remains to be elucidated.

AB - It is not clear how and whether terrestrial amphibians handle NaCl transport in the distal nephron. Therefore, we studied ion transport in isolated perfused collecting tubules and ducts from toad, Bufo bufo, by means of microelectrodes. No qualitative difference in basolateral cell membrane potential (Vbl) was observed between tubules and ducts in response to ion substitutions, inhibitor and agonist applications. Cl- substitution experiments indicated a small Cl- conductance in the basolateral membrane. The apical membrane did not have a significant Cl- conductance. Luminal [Na+] steps and amiloride application showed a small apical Na+ conductance. Arginine vasotocin depolarized Vbl. The small apical Na+ conductance indicates that the collecting duct system contributes little to NaCl reabsorption when compared to aquatic amphibians. In contrast, Vbl rapidly depolarized upon lowering of [Na+] in the bath, demonstrating the presence of a Na+-coupled anion transporter. [HCO3-] steps revealed that this transporter is not a Na+-HCO3- cotransporter. Together, our results indicate that a major task of the collecting duct system in B. bufo is not conductive NaCl transport but rather K+ secretion, as shown by our previous studies. Moreover, our results indicate the presence of a novel basolateral Na+-coupled anion transporter, the identity of which remains to be elucidated.

U2 - 10.1016/j.cbpb.2003.11.015

DO - 10.1016/j.cbpb.2003.11.015

M3 - Journal article

C2 - 15123195

SN - 1095-6433

VL - 137

SP - 585

EP - 595

JO - Comparative Biochemistry and Physiology A

JF - Comparative Biochemistry and Physiology A

IS - 3

ER -