1. A therapeutic or prophylactic agent against gastrointestinal diseases, comprising a peptide with the amino acid sequence Ser-Ser-Ser-Arg or a pharmaceutically acceptable salt thereof as an active ingredient. A therapeutic agent or prophylactic against gastrointestinal diseases, comprising as active ingredients a combination of the following components (a) and (b) :( a) a peptide with the amino acid sequence Ser-Ser-Ser-Arg or a pharmaceutically acceptable salt thereof； and (b) a peptide with the amino acid sequence of Phe-Gly-Leu-Met-NH or a pharmaceutically acceptable salt thereof. 3. The therapeutic agent or prophylactic against gastrointestinal diseases according to claim 1 or 2, wherein the gastrointestinal disease is a peptic ulcer or inflammatory gastrointestinal disease, a gastrointestinal disease caused by abnormal mucosal permeability, acquired digestive and absorption disorders, caused by damage to the gastrointestinal tract due to resection of the stomach and intestines, irradiation or action of the drug or congenital indigestion and suction aniya.4. A therapeutic agent or prophylactic against gastrointestinal diseases according to claim 1 or 2, wherein its dosage form is an oral preparation. A method for treating or preventing gastrointestinal diseases, comprising administering to a patient in need thereof a therapeutically effective amount of a peptide with the amino acid sequence Ser-Ser-Ser-Arg or a pharmaceutically acceptable salt thereof. 6. The method of treatment of sludge1. Терапевтическое средство или профилактическое средство против желудочно-кишечных заболеваний, содержащее пептид с аминокислотной последовательностью Ser-Ser-Ser-Arg или его фармацевтически приемлемую соль в качестве активного ингредиента.2. Терапевтическое средство или профилактическое средство против желудочно-кишечных заболеваний, содержащее в качестве активных ингредиентов комбинацию следующих компонентов (а) и (b):(a) пептид с аминокислотной последовательностью Ser-Ser-
