Characteristics of deslanoside-induced modulation on jejunal contractility.

To characterize the dual effects of deslanoside on the contractility of jejunal smooth muscle. Eight pairs of different low and high contractile states of isolated jejunal smooth muscle fragment (JSMF) were established. Contractile amplitude of JSMF in different low and high contractile states was selected to determine the effects of deslanoside, and Western blotting analysis was performed to measure the effects of deslanoside on myosin phosphorylation of jejunal smooth muscle. Stimulatory effects on the contractility of JSMF were induced (45.3% ± 4.0% vs 87.0% ± 7.8%, P < 0.01) by deslanoside in 8 low contractile states, and inhibitory effects were induced (180.6% ± 17.8% vs 109.9% ± 10.8%, P < 0.01) on the contractility of JSMF in 8 high contractile states. The effect of deslanoside on the phosphorylation of myosin light chain of JSMF in low (78.1% ± 4.1% vs 96.0% ± 8.1%, P < 0.01) and high contractile state (139.2% ± 8.5% vs 105.5 ± 7.34, P < 0.01) was also bidirectional. Bidirectional regulation (BR) was abolished in the presence of tetrodotoxin. Deslanoside did not affect jejunal contractility pretreated with the Ca(2+) channel blocker verapamil or in a Ca(2+)-free assay condition. The stimulatory effect of deslanoside on JSMF in a low contractile state (low Ca(2+) induced) was abolished by atropine. The inhibitory effect of deslanoside on jejunal contractility in a high contractile state (high Ca(2+) induced) was blocked by phentolamine, propranolol and L-NG-nitro-arginine, respectively. Deslanoside-induced BR is Ca(2+) dependent and is related to cholinergic and adrenergic systems when JSMF is in low or high contractile states.