Electrophysiological study of inner medullary collecting duct of hamsters.
The electrophysiological properties of the hamster mid-inner medullary collecting duct (IMCD2) cells were examined in isolated and perfused preparations by intracellular impalement with conventional 1 mol/l KCl microelectrodes and cable analysis. The transmural voltage (VT) was not different from 0 mV, while the basolateral transmembrane voltage (VB) was -81.7 +/- 0.91 mV (n = 221). The transmural resistance (RT) was 109 omega cm2, indicating that the IMCD2 is composed of tight epithelia. The fractional apical membrane resistance (fRA) was 0.98 +/- 0.003 (n = 10). Abrupt changes in the luminal concentration of Na+, K+ or Cl- did not alter the apical membrane voltage (VA) or VT, and neither 2 mmol/l Ba2+ nor 10 mumol/l amiloride in the lumen affected VA and VT. Moreover, pretreatment of hamsters with deoxycorticosterone acetate (5 mg/kg, s.c.) for 10-14 days caused only a very small change in VT in the negative direction. Amiloride in the lumen increased RT and increased the voltage divider ratio very slightly. However, an abrupt increase in K+ concentration in the bath from 5 mmol/l to 50 mmol/l or addition of 2 mmol/l Ba2+ to the bath depolarized the basolateral membrane by 39 mV and 29 mV, respectively. In the presence of 2 mmol/l Ba2+ in the bath, a reduction of HCO3- concentration from 25 mmol/l to 2.5 mmol/l depolarized VB by 20.4 mV. No Cl- conductance was demonstrated in the basolateral membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
Imai
M
M
Department of Pharmacology, National Cardiovascular Center, Osaka, Japan.
Yoshitomi
K
K
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology; D006224:Cricetinae; D004553:Electric Conductivity; D007684:Kidney Tubules / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000502:physiology*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism
D001639:Bicarbonates; D015221:Potassium Channels; D015222:Sodium Channels; D001464:Barium; D010042:Ouabain; D000584:Amiloride; D011188:Potassium