Intracellular Na+ activities in Aplysia gut: Effects of transport inhibitors on the Na+ pump

Na+ absorption by the Aplysia californica foregut is effected through an ac tive Naf transport mechanism located in the basolateral membrane of the epi thelial absorptive cells. Since Cl- absorption by the Aplysia gut has been shown to be very different from that demonstrated in vertebrate gut, the pr esent study was undertaken to discern if Na+ transport was also different f rom that observed in vertebrate preparations. Utilizing microelectrode tech nique, it was demonstrated that intracellular Na+ activity is below electro chemical equilibrium in the Aplysia absorptive cells and that amiloride, ou abain, Ba2+ or Cd2+ changed this asymmetry in Na+ electrochemical potential . Neither bumetanide, furosemide or chlorothiazide had any effect on intrac ellular Na+ activities, mucosal membrane potentials or transepithelial pote ntials in the Aplysia gut preparation. These results are consistent with th e operation of a basolateral Na+/K+ pump. (C) 1999 Elsevier Science Inc. Ai l rights reserved.