Irisin Relaxes Rat Trachea via K Channels, K Channels, and BK Channels.

BACKGROUND

This study aimed to investigate the effects of irisin on rat tracheal smooth muscle contraction-relaxation responses and the roles of voltage-gated potassium (K) channels, ATP-sensitive potassium (KATP) channels, and large-conductance calcium-activated potassium (BK) channels in these effects.

METHODS

Isometric contraction and relaxation responses of tracheal segments were measured using the tissue bath method. Submaximal contractions were induced by ACh (10 M) or KCl (60 mM), and then concentration-response curves of irisin (10 to 10 M) were obtained. For the temporal control, a double-distilled water group was formed. ACh and irisin were added to the baths after tracheal segments were incubated with 4-AP (K channel blocker), glibenclamide (K channel blocker), TEA, and iberiotoxin (BK channel blockers) to assess the role of K+ channels. In addition, a vehicle group was performed for the solvent dimethyl sulfoxide (DMSO).

RESULTS

Irisin exhibited the relaxant effects in tracheal segments precontracted with both ACh and KCl at concentrations of 10-10 M (p<0.05). Besides, incubations of 4-AP, glibenclamide, TEA, and iberiotoxin significantly inhibited the irisin-mediated relaxation (p<0.05), whereas DMSO incubation did not modulate irisin responses (p>0.05).

CONCLUSION

In conclusion, the first physiological results on the relaxant effects of irisin in rat trachea were obtained. Our findings demonstrated that irisin mediates concentration-dependent relaxation in rat tracheas. Moreover, the present study reported for the first time that irisin-induced bronchorelaxation is associated with the activity of the K+ channels.