This study compares the in vivo effect of exogenous administration of prostaglandin E2 (30 micrograms/kg) and its precursor, arachidonic acid (30 micrograms/kg), with the effect of indomethacin (5 mg/kg) on the 6-[3H]thymidine uptake of antral mucosa of mice by autoradiographical methods. Likewise, the effect of somatostatin (30 micrograms/kg) on 6-[3H]thymidine uptake is studied. Evaluation of the number of labeled cells, in the histological sections of the gastric mucosa, showed that arachidonic acid, prostaglandin E2, and somatostatin induced an increase in the number of labeled cells (107, 44, and 45%, respectively), while indomethacin induced a decrease of 32% compared to the control group. These results suggest that prostaglandins may mediate stimulatory effects on thymidine uptake of gastric mucosa cells in the first step after drug administration.