Disclosed is a substance which can prevent or treat a disease associated with the secretion of an acid. A calcium receptor activator is used as an active ingredient of a promoter for the bicarbonate secretion in a gastrointestinal tract. Examples of the calcium receptor activator include γ-Glu-X-Gly [wherein X represents an amino acid or an amino acid derivative], γ-Glu-Val-Y [wherein Y represents an amino acid or an amino acid derivative], γ-Glu-Ala, γ-Glu-Gly, γ-Glu-Cys, γ-Glu-Met, γ-Glu-Thr, γ-Glu-Val, γ-Glu-Orn, Asp-Gly, Cys-Gly, Cys-Met, Glu-Cys, Gly-Cys, Leu-Asp, γ-Glu-Met(O), γ-Glu-y-Glu-Val, γ-Glu-Val-NH2, γ-Glu-Val-ol, γ-Glu-Ser, γ-Glu-Tau, γ-Glu-Cys(S-Me)(O), γ-Glu-Leu, γ-Glu-Ile, γ-Glu-t-Leu and γ-Glu-Cys(S-Me).
