Provided is an agent having an action on a transcellular ion transporter in the intestinal tract, the agent containing a bacterium of the genus Bifidobacterium or the genus Lactobacillus, or a treated product thereof, with the proviso that the case where the ion transporter is a chloride channel and the action is inhibition; the case where the ion transporter is Na+K+Cl− cotransporter (NKCC1) and the action is inhibition; the case where the bacterium is Bifidobacterium infantis 35624; and the case where the bacterium is Lactobacillus salivarius UCC118 are excluded. The agent of the present invention is useful in activation of chloride channels, prevention or treatment of renal diseases, and/or promotion of defecation, and therefore, usable as a medicament, a supplement, etc.