Fig. 3. Relation between regulatory myosin light-chain (rMLC) phosphorylation and time during smooth muscle protein phosphatase assay conditions (adenosine triphosphate depletion with wortmannin) during exposure to either Ca²⁺alone (3.2 μm) or Ca²⁺(3.2 μm) with 10 μm acetylcholine and 10 μm guanosine triphosphate (n = 7). Values are mean ± SD and are expressed as absolute values (A ) or as a percentage of initial values (B ). Dashed line in (A ) denotes the mean baseline phosphorylation value (before exposure to calcium) of 11 ± 4%. Lines in the lower panel represent nonlinear regression of mean values fit to a monoexponential relation (equation 1).