Anti-gastrone and anti-urogastrone sera were obtained from rabbits which were immunized with gastrone extracted from human gastric juice and with urogastrone extracted from urine of pregnant women. Using these anti-sera, the origins and locations of Salivogastrone (SG. in the saliva), Gastrone (GO. in gastric juice) and Urogastrone (UG. in urine) were investigated by serial application of gel diffusion method and fluorescent antibody method, and the mutual relationship between these was studied. As a result, it was suggested that SG is almost identical to GO and that SG, GO and UG have partially the same characteristics. It was also suggested that GO existed in the salivary gland, in the neck of the gastric glandular cell, in the duodenum, in the brushborder and Goblet cells of the upper part of the jujunum, and also in the pancreas. Now, using the 3 types of gastrone, the inhibitory mechanism of gastric secretion was studied, the results of which are as follows: 1. When ~81SG and UG labelled with I TM were injected to rats, it was found that, unlike PSi-labelled human serum albumin and PSL-labelled sodium iodide, these two gastrone were accumulated preferentially to the stomach, and, besides, the accumulation reached maximum 180 minutes after SG infection and 60 minutes after UG infection, indicating the difference in the organ distribution pattern between SG and UG. 2. Gastrone inhibited carbonic anhydrase activity of rat stomach mucosa. 3. Gastrone exerted its effect on histamine release in the inverse way gastrine or cortisone. 4. When injected to feeding rats, gastrone depressed histidine decarboxylase activity to the half of the preinjection activity of rat stomach mucosa. When injected to fasting rats, a large dose of gastrone depressed histidine decarboxylase activity, whereas a small dose of gastrone did not influence on the activity. 5. Electron microscopic findings of gastric parietal cells of the rat injected with gastrone was found similar to those injected with atropine. 6. Phase contrast microscopic study after adding gastrone to rat parietal ceils revealed atrophy of the nucleus and the cytoplasma, and destruction, and degeneration of the mitochondria. The above described results suggest that gastrone exert its inhibitory effect on the gastric secretion at cellular as well as enzyme level. Further studies such as the elucidation of the chemical structure and the assay of gastrone are required at least for the thorough clarification of gastrone's mode of action. Reference :