Microwave irradiation is effective in the rapid fixation of gastric mucosa for determination of the prostaglandin content.

The gastric mucosal content of prostaglandin (PG) E2, 6-keto PGF1 alpha, and thromboxane (TX) B2 was determined by radioimmunoassay in unfed rats. The stomach was removed, and gastric mucosal specimens were prepared by microwave irradiation of the 1) intact stomach, 2) frozen stomach, 3) separated frozen glandular portion, 4) frozen gastric mucosa separated from the stomach wall, and 5) separation of frozen gastric mucosa with no microwave irradiation. Procedure 1 resulted in PGE2, TXB2, and 6-keto PGF1 alpha levels of 0.75, 2.33, and 3.04 ng/g tissue in the fundus, and 0.33, 1.92, and 1.76 ng/g tissue in the antrum, respectively. In procedures 2-4 these values were much higher, indicating that the PG content of the gastric mucosa is liable to be changed by various artificial procedures, such as freezing and surgical and mechanical handling. In procedure 5, values of PG contents were quite unreliable. These results suggest that microwave irradiation immediately after removal of the stomach may be the most reliable procedure for the accurate determination of the PG content of the gastric mucosa in vivo.