Prostaglandin concentrations and prostaglandin synthetase activity in N-nitrosomethylurea-induced rat mammary adenocarcinoma.

A comparison of tissue concentrations and biosynthesis of prostaglandin (PG)E2, PGF2 alpha, 6-keto-PGF1 alpha (degradation production of PGI2) and thromboxane (TX)B2 (degradation product of TXA2) was made in normal mammary glands obtained from virgin female Sprague-Dawley rats and in N-nitrosomethylurea (NMU)-induced mammary adenocarcinomas. The tissue concentrations (ng/g wet weight) of all 4 compounds were significantly higher in the NMU-induced tumor than in normal mammary tissue: PGE2, 210 +/- 37 vs 25 +/- 6; PGF2 alpha, 287 +/- 48 vs 23 +/- 8; 6-keto-PGF1 alpha, 294 +/- 42 vs 31 +/- 8; and TXB2, 260 +/- 49 vs 27 +/- 5 (mean +/- S.E.M.). Microsomal prostaglandin synthetase activity in NMU-induced tumors was also significantly higher than in normal tissue for all but 6-keto-PGF1 alpha: PGE2, 226 +/- 16 vs 50 +/- 9; PGF2 alpha, 28 +/- 3 vs 4 +/- 1; 6-keto-PGF1 alpha, 14 +/- 2 vs 11 +/- 2; and TXB2, 17 +/- 1 vs 10 +/- 1 ng/mg protein (mean +/- S.E.M.). There was no apparent relationship between either tumor size or age and the ability of microsomal enzyme to synthesize prostaglandins, although the content of prostaglandins extracted from tumor tissue was inversely related to the tumor size.