Selective inhibition of arachidonate 5-lipoxygenase by novel acetohydroxamic acids: effects on bronchial anaphylaxis in anaesthetized guinea-pigs.

1. The effect of a novel series of orally-active acetohydroxamic acid inhibitors of arachidonate 5-lipoxygenase on 'leukotriene-dependent' anaphylactic bronchoconstriction has been investigated in anaesthetized, pump-ventilated guinea-pigs actively sensitized to ovalbumin (OA). In a complementary series of experiments, the pharmacokinetics of these compounds in the plasma compartment following oral administration to guinea-pigs has also been investigated. 2. In animals pretreated with mepyramine (2 mg kg-1, i.v.) and indomethacin (10 mg kg-1, i.v.) and challenged with antigen aerosol (OA 10 mg ml-1; 5 s) compounds BW A4C, BW A137C and BW A797C (10-200 mg kg-1, p.o., 1 h pre-challenge) markedly reduced that component of anaphylactic bronchoconstriction shown to be 'leukotriene-dependent'. 3. The maximum degree of inhibition (up to 75%) of 'leukotriene-dependent' anaphylactic bronchoconstriction by these three compounds was equivalent to that seen with the leukotriene antagonist FPL 55712 (10 mg kg-1, i.v.). 4. The peak levels of unchanged acetohydroxamic acids in the plasma compartment occurred 0.5 h after their oral administration and were as follows: BW A4C: 11.3 +/- 3.9; BW A137C: 7.6 +/- 2.4; BW A797C: 3.9 +/- 1.3 micrograms ml-1 plasma. 5. The inhibition by BW A4C and BW A137C (50 mg kg-1, p.o.) of 'leukotriene-dependent' anaphylactic bronchospasm persisted for up to 3 and 4 h respectively but did not extend to 6 h. The decline in inhibitory activity paralleled the fall in the concentration of unchanged drug in the plasma compartment over this time period.(ABSTRACT TRUNCATED AT 250 WORDS)