Effect of lobaric acid on cysteinyl-leukotriene formation and contractile activity of guinea pig taenia coli.

Lobaric acid, a constituent of the lichen Stereocaulon alpinum, was investigated for effects on the smooth muscle taenia coli from guinea pigs. Inhibitory effects of lobaric acid on spontaneous contractile activity and on contractile activity stimulated by ionophore A23187 were studied. In addition, the activity of lobaric acid on ionophore-induced generation of cysteinyl-leukotrienes in taenia coli was determined by enzyme immunoassay. Lobaric acid significantly reduced spontaneous contractile activity of the muscle and inhibited contractions caused by ionophore A23187 with an effective dose of 5.8 microM. Increased contractility caused by leukotriene D4 was not influenced by lobaric acid. Lobaric acid inhibited the formation of cysteinyl-leukotrienes as determined by enzyme immunoassay with an effective dose of 5.5 microM.