Effects of removal of Na(+) and Cl(-) on spontaneous electrical activity, slow wave, in the circular muscle of the guinea-pig gastric antrum.
In the circular muscle of the guinea-pig gastric antrum, a decrease in the external Na(+) to less than 20 mM produced depolarization of the membrane with transient prolongation of the slow wave. This was followed by a high rhythmic activity. The activity was inhibited by reapplication of Na(+) before recovery. The depolarization in Na(+)-deficient solution was prevented and rhythmic activity continued at about 5/min for at least 6 min by simultaneous removal of K(+), Ca(2+), or Cl(-). After exposure to a Na(+)- and Cl(-)-deficient solution for a few minutes, reapplication of the Na(+) in Cl(-)-deficient solution inhibited generation of the slow wave until Cl(-) reapplication. Similar results were obtained when Na(+) and Cl(-) were reapplied in the absence of K(+) after exposure to a Na(+)-, K(+)-free, and Cl(-)-deficient solution, although the inhibition was weaker than Na(+) reapplication in a Cl(-)-deficient solution. In the presence of furosemide or bumetanide, a strong inhibition of activity was produced by the reapplication of Na(+) and Cl(-) after exposure to an Na(+)- and Cl(-)-deficient solution. A hypothesis is presented that intracellular Ca(2+) concentration ([Ca(2+)](i)) is the most important factor determining the generation and frequency of the slow wave and that [Ca(2+)](i) is regulated by the Na(+) concentration gradient across the plasma membrane. The recovery of the Na(+) concentration gradient by Na(+) reapplication after removal of Na(+) and Cl(-) is mainly controlled by a Na(+)-K(+)-Cl(-) co-transport.
Tomita
T
T
Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, 470-1192 Japan. ttomita@fujita-hu.ac.jp
Hata
T
T
D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism / Q000494:pharmacology*; D004232:Diuretics / Q000494:pharmacology*; D005260:Female; D005665:Furosemide / Q000494:pharmacology; D006168:Guinea Pigs; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D011706:Pyloric Antrum / Q000502:physiology*; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology*; D028021:Sodium-Potassium-Chloride Symporters
D002352:Carrier Proteins; D002712:Chlorides; D004232:Diuretics; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D005665:Furosemide; D012964:Sodium; D011188:Potassium; D002118:Calcium