The Amiloride Inhibitable Na+ Conductance of Rat Colonic Crypt Cells Is Suppressed by Forskolin

Pflugers Arch. 1996 Apr;431(6):984-6. doi: 10.1007/s004240050095.

Abstract

Previously we have shown that mid crypt cells of corticoid treated rats possess an amiloride inhibitable Na+ conductance (NAC) and show an increased Cl- conductance when stimulated by prostaglandin or the second messenger cAMP. The NAC is supposed to determine the magnitude of NaCl absorption. The Cl- conductance defines the magnitude of NaCl secretion. In the present whole cell (WC) patch clamp study we have examined whether the amiloride (3 "mu"mol/l) inhibitable NAC is downregulated when the Cl- conductance is increased by forskolin (5 "mu"mol/l, n=20) or the phosphodiesterase inhibitor IBMX (1 mmol/l, n=5). Under control conditions the amiloride inhibitable NAC was 2.7+/-0.4 nS. Forskolin depolarized the voltage from -58+/-2.0 to -48+/-1.9 mV and enhanced the WC conductance by 3.25+/-0.6 nS in these cells. The amiloride inhibitable NAC was reduced to 0.38+/-0.2 nS. These data confirm that forskolin enhances the Cl- conductance in these cells and they show for the first time that the Na+ conductance is reduced simultaneously. Thus the cells are able to change the direction of NaCl transport from absorption to secretion.

MeSH terms

  • 1-Methyl-3-isobutylxanthine / pharmacology
  • Amiloride / pharmacology*
  • Animals
  • Chloride Channels / drug effects
  • Chloride Channels / metabolism
  • Chlorides / metabolism
  • Colforsin / pharmacology*
  • Colon / cytology
  • Colon / drug effects
  • Colon / metabolism*
  • Down-Regulation
  • Electric Conductivity
  • Ion Transport / drug effects
  • Membrane Potentials / drug effects
  • Rats
  • Sodium / metabolism*
  • Sodium Channel Blockers
  • Sodium Channels / drug effects
  • Sodium Channels / metabolism

Substances

  • Chloride Channels
  • Chlorides
  • Sodium Channel Blockers
  • Sodium Channels
  • Colforsin
  • Amiloride
  • Sodium
  • 1-Methyl-3-isobutylxanthine