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Early radiation toxicity is characterized by nausea and vomiting. We have previously shown that gastric emptying, gastric motility, and gastric secretion were suppressed after total body exposure to irradiation. In the present studies, we evaluated the relation between vomiting and gastric function in nine rhesus monkeys and explored the possible role of prostaglandins (PG) in these phenomena. The concentration of PG in plasma and gastric juice was determined using a standard radioimmunoassay and gastric acid output was measured concurrently using a marker dilution technique. The animals were studied in the basal state and after total body exposure to 800 cGy 60Co delivered at a rate of 500 cGy/min. Acid output was abolished from 40 min to 2 h after irradiation but had returned to preirradiation levels 2 days later. Plasma PGE2 and PGI2 (as measured by 6-keto-PGF1 alpha determination) were not significantly modified by irradiation. In contrast, irradiation produced an immediate significant increase (P less than 0.05) in gastric juice concentration of PGE2 (318 +/- 80 to 523 +/- 94 pg/ml; mean +/- SE) and PGI2 (230 +/- 36 to 346 +/- 57 pg/ml); both had returned to basal levels 2 days later. Thus, an increase in gastric juice concentration of both PGE2 and PGI2 is associated with the radiation induced suppression of acid output.