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Ca(2+)‐independent change in phosphorylation of the myosin light chain during relaxation of ferret aorta by vasodilators.
Author(s) -
Suematsu E,
Resnick M,
Morgan K G
Publication year - 1991
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1991.sp018697
Subject(s) - forskolin , aequorin , myosin light chain kinase , phosphorylation , medicine , chemistry , endocrinology , calcium , atrial natriuretic peptide , myosin , vasodilation , contractility , calmodulin , biophysics , biology , stimulation , biochemistry
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.