The paradox of smooth muscle physiology.
Vascular smooth muscle tone is controlled by a balance between the cellular signaling pathways that mediate the generation of force (contraction) and the release of force (relaxation). The signaling events that activate contraction include Ca(2+)-dependent myosin light chain phosphorylation. The signaling events that mediate relaxation include the removal of a contractile agonist (passive relaxation) and activation of cyclic nucleotide-dependent signaling pathways in the continued presence of a contractile agonist (active relaxation). The major questions that remain in contractile physiology include (1) how is tonic force maintained when intracellular Ca(2+) levels and myosin light chain phosphorylation have returned to basal levels; and (2) what is the mechanism of cyclic nucleotide-dependent relaxation? This review focuses on these specific controversies surrounding the molecular mechanisms of contraction and relaxation of vascular smooth muscle.
Woodrum
D A
DA
Institute for Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, Augusta, GA, USA.
Brophy
C M
CM
D000818:Animals; D006801:Humans; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009712:Nucleotides, Cyclic / Q000494:pharmacology; D010766:Phosphorylation; D015398:Signal Transduction
D009712:Nucleotides, Cyclic