The effects of ecabet sodium (ecabet), 12-sulfodehydroabietic acid monosodium salt, on gastric mucin biosynthesis in rat antrum were compared with those in the corpus. Intragastric administration of ecabet significantly increased [3H]glucosamine incorporation into antral mucin as well as into corpus mucin during five successive hours of organ culture. In contrast, mucin biosynthesis in either antrum or corpus was not susceptible to the addition of ecabet to the culture medium. Ecabet-induced stimulation of prostaglandin E2 production in the antrum was essentially the same as that seen in the corpus. In antrum treated with 100 mg/kg ecabet, immunoreactivity with three distinct anti-mucin monoclonal antibodies was found not only in the specific mucus-producing cells, but also in the secreted mucus present at the surface gel layer. These results suggest that ecabet enhances the mucin metabolism, and this stimulation occurs in both the corpus and antrum, suggesting that ecabet might be a useful tool for the further clarification of the regulatory mechanism of antral mucin synthesis.