Water and electrolyte transport by the avian ceca.

In galliform birds with well developed ceca, these are functionally important components of the lower intestinal complex, which is capable as a whole of substantial, hormone-regulated homeostatic modification of mixed urine and intestinal luminal fluid before final excretion. Active Na+ transport drives Na-linked absorption of water and Cl- and secretion of K+; there are also lesser Na-independent components of the latter fluxes. These transport processes are appropriately enhanced by dehydration, Na depletion, or exogenous aldosterone.