THE EFFECT OF HYPOXIA ON ELECTRICAL AND CONTRACTILE PROPERTIES OF SMOOTH MUSCLES OF THE GUINEA PIG URETER

Aim. The effect of hypoxia on the electrical and contractile activities of smooth muscles cells (SMCs) of the guinea pig ureter was studied by the method of the double sucrose bridge.

Materials and methods. This method allows registering simultaneously parameters of the action potential (AP) and the contraction of SMCs, caused by an electrical stimulus.

Results. It was found that lowering the oxygen content in the perfusion solution for 10 min resulted to an increase of electrical and contractile activity of ureteral SMCs. Addition of tetraethylammonium chloride (TEA, 5 mM) – nonselective blocker of potassium membrane conductance – in hypoxic conditions causing an additional increase in the amplitude of the AP, duration of the AP plateau and the contractile responses of smooth muscles. Thus, the hypoxia decreased the potassium membrane conductance of ureteral SMCs. Inhibition of the effect of the α1 -adrenergic receptors agonist phenylephrine (PE, 10 mM) on the electrical and contractile properties of SMCs in hypoxic condition indicate the involvement of the protein kinase C-dependent signaling system in effects of hypoxia. Pretreatment of ureteral smooth muscles with bumetanide (100 mM) – selective inhibitor of Na+,K+,2Cl- - cotransporter (NKCC) – caused a decrease of the activating effect of hypoxia on the SMCs of guinea pig ureter.

Conclusion.Thus, the impact of hypoxia on the regulation of electrical activity and contractions of smooth muscles of guinea pig ureter may be due to changes in ion permeability of membranes SMCs and operation of ion-transporting systems. 

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