Fig. 9.

Suppression of SNAP-induced relaxation by inflammation and complete reversal of inhibition by blockade of iNOS and PDE1 activity. Longitudinal muscle cells isolated from colons of control and TNBS-treated mice (A) or from muscle strips cultured in the presence of IL-1β (10 ng/ml) (B) or TNF-α (1 nM) (C) for 48 hours were treated with different concentrations of SNAP for 5 minutes and carbachol for 30 seconds to measure initial Ca²⁺-dependent contraction. In some experiments, muscle strips were cultured with IL-1β or TNF-α in the presence of both iNOS (1400W, 10 µM) and PDE1 (vinpocetine, 50 µM) inhibitors. Smooth muscle cell contraction was measured by scanning micrometry, and relaxation was expressed as the percent inhibition of carbachol-induced contraction. Values are the means ± S.E.M. of five to six experiments. **P < 0.01, significant inhibition of SNAP-induced relaxation. (D) Longitudinal muscle cells isolated from colons of control and TNBS-treated mice or from muscle strips cultured in the presence of IL-1β (10 ng/ml) or TNF-α (1 nM) for 48 hours were treated with PDE-resistant 8-Bromo-cGMP (10 µM) for 5 minutes and carbachol (1 µM) for 30 seconds to measure initial Ca²⁺-dependent contraction. Smooth muscle cell contraction was measured by scanning micrometry, and relaxation was expressed as the percent inhibition of carbachol-induced contraction. Values are the means ± S.E.M. of four experiments.