title: Ca(2+)-independent change in phosphorylation of the myosin light chain during relaxation of ferret aorta by vasodilators.
abstract: 1. The effects of the vasodilators atrial natriuretic peptide (ANP) and forskolin were determined on isometric force, intracellular ionized Ca2+ concentration ([Ca2+]i) as indicated by aequorin, and myosin light chain (MLC) phosphorylation in ferret aorta. 2. Atrial natriuretic peptide (10(-7) M) inhibited intrinsic tone with an associated significant decrease in [Ca2+]i. ANP also inhibited the contraction induced by KCl with a significant decrease in [Ca2+]i. MLC phosphorylation induced by KCl was inhibited by ANP. 3. Forskolin (10(-6) M) decreased the intrinsic tone without significantly decreasing [Ca2+]i, although MLC phosphorylation was significantly decreased. 4. A calcium-force curve was constructed by plotting the calibrated aequorin light signal against the resulting force. The control (potassium-generated) calcium-force curve was not shifted by ANP, but was significantly shifted to the right by forskolin. Forskolin also shifted the phosphorylation-calcium curve to the right without changing the phosphorylation-force curve. 5. We conclude that the vasodilatory effect of ANP on vascular smooth muscle is mainly due to a decrease in [Ca2+]i. On the other hand, the effect of forskolin is via both a decrease in [Ca2+]i and a change in the Ca2+ requirement for MLC phosphorylation.
authors.affiliation: Cardiovascular Division, Charles A. Dana Research Institute, Boston, MA.
authors.forename: E
authors.initials: E
authors.lastname: Suematsu
authors.forename: M
authors.initials: M
authors.lastname: Resnick
authors.forename: K G
authors.initials: KG
authors.lastname: Morgan
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D046508:Culture Techniques; D005289:Ferrets; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects* / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009218:Myosins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects
chemical_list: D005576:Colforsin; D009320:Atrial Natriuretic Factor; D009218:Myosins; D002118:Calcium