MK 571 (Synonyms: L-660,711)

MK 571 (L-660,711) is a novel potent and selective antagonist of leukotriene D4 receptor with Ki values of 0.22 nM and 2.1 nM in guinea pig and human lung membranes, respectively [1]. MK 571 is also a specific inhibitor of the multidrug resistance protein 1 (MRP1) [2].

Leukotriene D4 (LTD4) is one of the leukotrienes and is released by basophils. LTD4 induces the contraction of smooth muscle and increases vascular permeability. Cysteinyl leukotriene receptor 1 (cysLT1 receptor, LTD4 receptor) is a G protein-coupled receptor activated by LTD4 [3].

MK 571 (L-660,711) is a potent, selective and orally active leukotriene D4 receptor antagonist. MK 571 competitively antagonized contractions of guinea pig trachea and ileum induced by LTD4 (pA2 values, 9.4 and 10.5) and LTE4 (pA2 values, 9.1 and 10.4) , and antagonized contractions of human trachea induced by LTD4 with pA2 value of 8.5 [1].

In anesthetized guinea pigs, MK 571 antagonized bronchoconstriction induced by LTC4, LTD4, and LTE4 [1]. In mice, MK 571 (1, 10, 100 mg/kg) inhibited inflammatory cell infiltration in the bronchoalveolar lavage in a dose-dependent way with maximal inhibition of 90%. MK 571 also inhibited bronchial hyperreactivity and reduced lung microvascular leakage by 22% at 10 mg/kg [3].

References:
[1].  Jones TR, Zamboni R, Belley M, et al. Pharmacology of L-660,711 (MK-571): a novel potent and selective leukotriene D4 receptor antagonist. Can J Physiol Pharmacol, 1989, 67(1): 17-28.
[2].  Vellenga E, Tuyt L, Wierenga BJ, et al. Interleukin-6 production by activated human monocytic cells is enhanced by MK-571, a specific inhibitor of the multi-drug resistance protein-1. Br J Pharmacol, 1999, 127(2): 441-448.
[3].  Blain JF, Sirois P. Involvement of LTD(4) in allergic pulmonary inflammation in mice: modulation by cysLT(1)antagonist MK-571. Prostaglandins Leukot Essent Fatty Acids, 2000, 62(6): 361-368.