title: Na microelectrode study of pathways of Na entry into Amphiuma intestinal absorptive cells.
abstract: To define the pathways of Na+ entry into intestinal villus cells, intracellular Na+ activity (aiNa) was measured in Amphiuma duodenum using conventional and Na-sensitive microelectrodes. Replacement of Na+ in the luminal medium reduced aiNa rapidly; replacement of Na+ in the serosal medium caused a slow decline of aiNa. Hence, mucosal and serosal membranes are both permeable to Na+. Ouabain addition to the serosal medium caused aiNa to increase over 4 h. When Na+ was present only in the mucosal medium and Na+ transport was inhibited with ouabain, aiNa increased over 4 h. With galactose or valine (20 mM) in the mucosal medium aiNa was greater at 2 h relative to paired control tissues. The gain in aiNa was unaffected by replacement of luminal medium Cl- with gluconate or exposure to 1 mM furosemide or amiloride. Amiloride, at 1 mM, was detected by the Na-sensitive neutral carrier. Over a wide range of Na+ concentrations in the luminal medium the rate of Na+ entry across the mucosal membrane correlated strongly (r = 0.95) with the electrochemical gradient for Na+ across the luminal membrane. It is concluded that aiNa of urodele intestinal cells is maintained at a low level by the operation of a Na+-K+ pump. Na+ entry across the luminal membrane occurs by diffusion and by the cotransport with sugars and amino acids. Luminal NaCl cotransport and Na+-H+ exchange do not appear to contribute to Na entry to a measurable extent but it is possible that these transport processes operate at a slow rate, but were inhibited secondary to inhibition of the Na-K pump.
mesh_terms: D000042:Absorption; D000818:Animals; D001834:Body Water / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D004058:Diffusion; D005690:Galactose / Q000494:pharmacology; D006859:Hydrogen / Q000378:metabolism; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology; D007474:Ion Exchange; D008839:Microelectrodes; D010042:Ouabain / Q000494:pharmacology; D012704:Serous Membrane / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D049992:Sodium Chloride Symporters; D027981:Symporters; D014562:Caudata; D014633:Valine / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; D049992:Sodium Chloride Symporters; D027981:Symporters; D010042:Ouabain; D006859:Hydrogen; D012964:Sodium; D014633:Valine; D002118:Calcium; D005690:Galactose