Sodium-dependent absorption of inorganic phosphate by the carp intestine.

Concentrative absorption of inorganic phosphate observed in the stripped and everted intestine of the carp disappeared, when Na concentration of the Ringer solution was reduced from 150 to 7 mM, or when orthophosphate was replaced with metaphosphate. Incubation in the Ringer solution gassed with N2 instead of O2 also resulted in loss of the Pi absorption. Dinitrophenol significantly decreased the unidirectional Pi flux from mucosa to serosa (Jms) and increased the flux from serosa to mucosa (Jsm). Ouabain also caused a significant decrease in Jms, whereas L-phenylalanine had no effect on Jms.