[Changes of potassium channel activity of hindlimb arterial smooth muscle cells in tail-suspended rats].

OBJECTIVE

To examine the change of potassium channel function in hindlimb arterial smooth muscle cells in tail-suspended rats and to elucidate the underlying electro-physiological mechanisms responsible for the depressed vascular responsiveness of hindlimb arteries induced by simulated weightlessness.

METHOD

The contractile responsiveness of femoral arterial rings of 1-wk and 4-wk tail-suspended rats to potassium channel blockers, tetraethylammonium chloride (TEA) and 4-aminopyridine (4-AP), were recorded, and the currents of large conductance calcium-dependent potassium channel (BK(Ca)) and voltage activated potassium channel (Kv) of vascular smooth muscle cells (VSMCs) in saphenous arteries from 1-wk tail-suspended rats were recorded using the whole cell recording mode of patch clamp technique.

RESULT

The femoral arteries from of 1-wk and 4-wk tail-suspended rats showed a decreased contractile response to 60 mM KCl, and the ratio of their contractile responses induced by TEA or 4-AP to their responses induced by 60 mM KCl increased significantly after 1-wk and 4-wk simulated weightlessness. However no difference was found between 1-wk and 4-wk tail-suspended rats. The whole cell current recording showed that BK(Ca) current densities and K(v) current densities of VSMCs in saphenous artery increased significantly after 1-wk simulated weightlessness.

CONCLUSION

The contractile response of hindlimb arteries to KCl decreased after simulated weightlessness. The activities of BK(Ca) and K(v) of smooth muscle cells in hindlimb arteries from tail-suspended rats increased, and these changes might be among the electro-physiological mechanisms involved in the depressed vasoreactivity of hindlimb arteries due to simulated weightlessness.