Transport Across the Invertebrate Intestine

Sodium-Phosphate Symport by Aplysia Californica Gut

“…Therefore, one of the reasons for studying the Aplysia gut was to provide evidence for the existence of a P i -transporter and, also to identify the nature of this transporter. When the Aplysia foregut was bathed in a P i -free (Table 1) or Cl --free (Gerencser, 1981;Gerencser, 1985) Na + -containing seawater media, the net active absorptive flux of Na + was equivalent to the SCC. This observation is interpreted as Na + being the only ion actively translocated, in a net sense, across the gut tissue.…”

The Cl− ATPase pump

“…The a Cl i values both before and after d-glucose addition were significantly less than those predicted by the electrochemical equilibrium for Cl À across the mucosal membrane. In the absence of Na + in the extracellular bathing solution, the mean a Cl i was 9.1 mM, which is also less than that predicted for electrochemical equilibrium for Cl À across the mucosal membrane [18,19]. Thus, one need not postulate an active transport mechanism for Cl À in the apical or mucosal membrane of the Aplysia foregut absorptive cell because Cl À transport across this membrane could be driven by the downhill mucosal to cytosol electrochemical potential gradient for Cl À .…”

Electrogenic proton-regulated oxalate/chloride exchange by lobster hepatopancreatic brush-border membrane vesicles

“…It was observed that 36 Cl -influx did respond to an inside-negative potential (Fig.·9) by an increased uptake during its incubation. With this arrangement there would be a secretion of Ox 2-from the vesicular interior in exchange for luminal Cl -that is further driven by the inside negative potential that is characteristic of epithelial cells (Gerencser, 1985). This secretion of Ox 2-would lead to its excretion unless it were recycled by the same antiporter.…”