PHARMACOLOGICAL PROFILE OF LEUKOTRIENES-E4, NORMAL-ACETYL-E4 AND OF 4 OF THEIR NOVEL OMEGA-OXIDATIVE AND BETA-OXIDATIVE METABOLITES IN AIRWAYS OF GUINEA-PIG AND MAN INVITRO

  • 1 December 1989
    • journal article
    • research article
    • Vol. 98 (4), 1406-1412
Abstract
The biological effects of metabolites of leukotriene E4 (LTE4) i.e. N-acetyl LTE4 (N-AcLTE4), 20-COOH-LTE4, 20-COOH-N-AcLTE4, as well as 18-COOH-19,20-dinor-LTE4 (dinor-LTE4) superfused strips of guinea-pig trachea (GPT) and lung parenchyma (GPP) in vitro. The actions of LTE4 were studied in isolated, superfused strips of human lung parenchyma (HP) and bronchus (HBr), in comparison with LTD4 and histamine. Effects of N-AcLTE4, the 20-carboxy metabolites, dinor-LTE4 and tetranor-LTE4 were also investigated in HBr. N-AcLTE4 (0.1-10 nmol) induced dose-related contractions of GPT and was approximately 100 times less active than LTD4 (3-100 pmol). In GPP, N-AcLTE4 (0.01-3 nmol) was equiactive with LTE4 (0.01-1 nmol) and approximately one order of magnitude less active than LTD4 (1-300 pmol). Contractions caused by N-AcLTE4 and LTE4 were very similar and approximately twice as sustained as those due to LTD4. LTE4 (0.1-30 nmol) contracted strips of HP and HBr and was about 2-3 orders of magnitude less active than LTD4. As in GPP, the effect of LTE4 was more protracted than that of LTD4. Actions of N-AcLTE4 were similar to those of LTE4 in HBr. 20-carboxy-LTE4, 20-carboxy-N-AcLTE4, dinor-LTE4 and tetranor-LTE4, all at 0.3-30 nmol, were inactive in GPT, GPP and HBr. Indomethacin (2.8 .mu.M) potentiated the effect of N-AcLTE4 in GPT, inhibited its contraction in GPP but did not affect that due to LTE4 in either HP or HBr. FPL 55712 (1.9 .mu.M) antagonised leukotriene-induced contractions in GPT, GP and HBr. In conclusion, the metabolism of LTD4 to LTE4 or N-AcLTE4 may represent a detoxification but not an inactivation of cysteinyl-containing leukotrienes, since both metabolites still retain considerable biological activity in guinea-pig and human airways in vitro. However, further metabolism of LTE4 and N-AcLTE4 appears to result in inactivation of leukotrienes.