Albaconol from the Mushroom Albatrellus confluens Induces Contraction and Desensitization in Guinea Pig Trachea

Abstract

The contraction and desensitization induced by albaconol and the influence of capsazepine, capsaicin and extracellular Ca²⁺ were investigated to see whether the actions were mediated via a specific VR receptor in guinea pig trachea spiral strips in vitro. Both albaconol and capsaicin were contractors of tracheal smooth muscle, but albaconol was not so potent as capsaicin, with -log (M) EC₅₀ values of 4.23 ± 0.18 (n = 10) and 7.33 ± 0.21 (n = 10) respectively. 2.5 μM capsazepine competitively antagonized the contractile response to albaconol and capsaicin. Albaconol increased the contraction induced by a low dose of capsaicin (10^-10 to 10^-9 M), but non-competitively antagonized the contraction induced by a high dose of capsaicin (10^-8 to 10^-3 M). Either albaconol (1 or 100 mM) or capsaicin (3 or 10 μM) was able to desensitize the isolated guinea pig bronchi to subsequent addition of albaconol. Capsazepine (5.0 μM) significantly prevented the desensitization induced by either albaconol (1 or 100mM) or capsaicin (3 or 10 μM). Extracellular Ca²⁺ was essential for albaconol to induce excitation, but it did not affect albaconol- or capsaicin-induced desensitization. In summary, the results from the present study suggest that albaconol induces contraction and desensitization of guinea pig trachea in vitro as a partial agonist for VR.

Key words

Albaconol - Albatrellus confluens - Polyporaceae - capsazepine - capsaicin - vanilloid receptor - guinea pig trachea - contraction

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