Effects of bacterial endotoxin on the contraction and relaxation responses of the rabbit cavernous smooth muscles

초록

Purpose: We evaluated effects of bacterial endotoxin during septicemia on contraction and relaxation responses of cavernous smooth muscles in rabbits. Materials and Methods: We performed isometric tension studies with norepinephrine (NE), endothelium-dependent and endothelium-independent vasodilators, and nonadrenergic noncholinergic (NANC)-selective electrical field stimulation on the muscle strips of control and endotoxin (lipopolysaccharide; LPS)-treated rabbits. To determine reversibility of the LPS effects on the cavernous smooth muscle, the contraction and relaxation studies were repeated after resting the strips for 1 day at 4C. We also investigated the effect of the nonspecific nitric oxide synthase (NOS) inhibitor (N-w-nitro-L-arginine methyl ester; L-NAME) and the selective immunologic MOS inhibitor (aminoguanidine) on reactivity of the strips to NE and acetylcholine. Results: Contractile response to NE was significantly (p <0.01) reduced in the cavernous smooth muscles from the systemically and locally LPS-treated rabbits, compared with control group. Both aminoguanidine and L-NAME markedly improved the diminished contraction of the strips. Relaxation response to endothelium-dependent agonists (acetylcholine and bradykinin) was significantly (p <0.05) decreased in the LPS-treated groups, compared with the control group but not to endothelium-independent vasodilators (papaverine and verapamil) and NANC-selective electrical field stimulation. L-NAME completely inhibited the relaxation response to acetylcholine in the control and LPS-treated groups but aminoguanidine did not. The impaired contraction and relaxation of the strips was completely restored after resting for 1 day. Conclusions: Bacterial endotoxin may cause non-endothelial overproduction of NO and inhibition of endothelium-derived NO production, which may contribute to impairment of contraction and relaxation of rabbit cavernous smooth muscles.

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