Competition of NO synthases and arginase in the airways hyperreactivity

The competition between arginases and NO synthases (NOS) for their common substrate L-arginine can be important in the airways hyperreactivity. We investigated the effect of the simultaneous modulation of arginase and NOS activities in allergen-induced airways hyperreactivity. We analysed the response of tracheal and lung tissue smooth muscle to histamine or acetylcholine after administration N(ω)-nitro-L-arginine methyl ester (L-NAME), aminoguanidine (AG) and N(ω)-hydroxy-L-arginine (NOHA) in the combinations in in vitro conditions. The results show the decrease of ovalbumin-induced hyperreactivity after inhibition of arginase activity with NOHA. A supplementation of L-arginine caused favourable effect on the airway smooth muscle response. We found the airway reactivity decrease on the whole if we used the combination of NOS and arginase inhibitors. The inhibition of both types of enzymes caused more expressive effect in tracheal smooth muscles. We recorded the difference in the response to histamine or acetylcholine. The simultaneous inhibition of iNOS (with AG) and arginase (with NOHA) evoked the most expressive effect. Results show the importance of competition of both types enzymes - NOS and arginase for the balance of theirs activities in the control of airways bronchomotoric tone in the conditions of the airways hyperreactivity.