Fig. 2.

SNAP-induced cGMP generation and muscle relaxation. (A) Longitudinal muscle cells were treated with different concentrations of SNAP in the presence or absence of Rp-cGMPS (10 µM) for 5 minutes. cGMP was measured in the presence of 100 µM IBMX by radioimmunoassay and expressed as pmol/mg protein above basal levels (0.22 ± 0.04 pmol/mg protein). Values are the means ± S.E.M. of four experiments. **P < 0.01, significant increase in SNAP-induced cGMP generation by Rp-cGMPS. (B) Longitudinal muscle cells isolated from colon were treated with different concentrations of SNAP in the presence or absence of Rp-cGMPS (10 µM) for 5 minutes followed by carbachol 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 (basal cell length: 95 ± 4 µm; carbachol-induced contraction: 31 ± 3% decrease in cell length). Values are the means ± S.E.M. of five to six experiments. **P < 0.01 significant inhibition in SNAP-induced relaxation by Rp-cGMPS.