Studies of prostaglandins and prostaglandin antagonists on bovine pulmonary vein in vitro

Abstract

Acetylsalicylic acid (ASA), indomethacin, sodium meclofenamate (FEN), phenylbutazone (PB), phloretin phosphates (PP), SC-19220, and diethylcarbamazine citrate (DECC) were screened against histamine, 5-hydroxytryptamine (5-HT), bradykinin, acetylcholine, and prostaglandins (PG) E 1, E 2, and F 2α to determine their specificity in antagonizing PG's on the bovine pulmonary vein. PG E 2 relaxed the smooth muscle preparation at low concentrations and induced contraction at higher concentrations. PG E 1 consistently evoked dose-related relaxations, whereas PG F 2α contracted the bovine pulmonary vein. Studies with inhibitors suggest that the different actions of prostaglandins could be mediated through different receptors. Sodium meclofenamate and PP dimer blocked PG E 2-induced contractions, whereas relaxations were not blocked. DECC inhibited the relaxant effect of PG E 2. DECC also antagonized histamine, 5-HT, and PG F 2α, suggesting the drug is rather non-specific. Phenylbutazone antagonized the actions of both PG E 2 and PG F 2α on the bovine pulmonary vein. By classifying receptors by antagonism the bovine pulmonary vein appears to contain PG E 2 (PP-type), PG E 2 (FEN-type), PG E 2 (PB-type), and PG F 2α (PB-type) receptors. An absence of SC-type PG-receptors is noted.