EFFECTS OF TETRAMETHYLPYRAZINE ON THE RELEASE OF PGI(2) AND TXA(2) INTHE HYPOXIC ISOLATED RAT-HEART

We examined the effect on 6-Keto-PGF(1a) and TXB(2) (the stable metabo lites of PGI(2) and TXA(2)) outflow of pretreatment with tetramethylpy razine in the hypoxic isolated rat heart. In control hearts, 6-Keto-PG F(1a) was increased from 185 +/- 46 pg/ml of baseline value to 335 +/- 76 pg/ml after 2 min of hypoxia and TXB(2) increased from 136 +/- 28 pg/ml of baseline value to 230 +/- 43 pg/ml at 20 min of hypoxia and 2 52 +/- 32 pg/ml after 5 min of reoxygenation. Pretreatment with tetram ethylpyrazine increased the 6-Keto-PGF(1a) concentration to 266 +/- 51 pg/ml (143% of control heart), 471 +/- 89 pg/ml (150% of control hear t) and 332 +/- 47 pg/ml (195% of control heart) at 15 min of normoxia, 2 min of hypoxia and 5 min of reoxygenation, respectively (p < 0.05 v s control). On the other hand, tetramethylpyrazine diminished the rele ase of TXB(2) to 78 +/- 21 pg/ml (174% of control heart), 160 +/- 30 p g/ml (144% of control heart), and 196 +/- 23 pg/ml (128% of control he art) at 15 min of normoxia, 20 min of hypoxia and 5 min of reoxygenati on, respectively (p < 0.05 vs control). These data show that pretreatm ent with tetramethylpyrazine enhances PGI(2) outflow and attenuates re lease of TXA(2) in the rat heart during normoxia, hypoxia and reoxygen ation.