title: Myosin light chain kinase phosphorylation in nitrovasodilator induced swine carotid artery relaxation.
abstract: Nitrovasodilators are hypothesized to induce smooth muscle relaxation by their metabolism to nitric oxide, which then activates soluble guanylyl cyclase, increases [cGMP], and activates cGMP-dependent protein kinase. cGMP-dependent phosphorylation is then proposed to decrease intracellular [Ca2+] ([Ca2+]i) and to reduce the Ca(2+)-sensitivity of contraction. We hypothesized that one component of decreased Ca(2+)-sensitivity, reduced Ca(2+)-sensitivity of MLC phosphorylation, was due to phosphorylation of myosin light chain kinase (MLCK) on the peptide site A. In the swine carotid artery, histamine (10 microM) stimulation increased aequorin-estimated [Ca2+]i, MLCK site A phosphorylation, MLC phosphorylation, and force. Subsequent addition of 100 microM nitroglycerin (NTG) or 100 microM sodium nitroprusside (NP) to histamine-stimulated tissues increased [cGMP], decreased both MLC phosphorylation and force, but did not significantly alter [cAMP], [Ca2+]i, or MLCK site A phosphorylation. Addition of NTG and NP alone to unstimulated tissues increased MLCK site A phosphorylation, but did not alter [Ca2+]i. In tissues preincubated with NP, subsequent histamine contraction was slowed compared with controls, however, this slowed rate of contraction appeared to result from an attenuation of histamine-dependent increases in [Ca2+]i. These data suggest that, in swine carotid artery, nitrovasodilators can decrease the Ca(2+)-sensitivity of MLC phosphorylation without increasing MLCK site A phosphorylation. Nitrovasodilators, per se, can induce site A MLCK phosphorylation, potentially by cGMP dependent activation of cAMP-dependent protein kinase.
authors.affiliation: Department of Internal Medicine, University of Virginia Health Science Center, Charlottesvile 22908, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: van Riper
authors.forename: N L
authors.initials: NL
authors.lastname: McDaniel
authors.forename: C M
authors.initials: CM
authors.lastname: Rembold
mesh_terms: D000331:Aequorin / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002339:Carotid Arteries / Q000187:drug effects* / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D018994:Myosin Light Chains / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism*; D005996:Nitroglycerin / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010449:Peptide Mapping; D010766:Phosphorylation; D013552:Swine; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D018994:Myosin Light Chains; D014665:Vasodilator Agents; D009599:Nitroprusside; D000331:Aequorin; D006632:Histamine; D000242:Cyclic AMP; D009219:Myosin-Light-Chain Kinase; D005996:Nitroglycerin; D006152:Cyclic GMP; D002118:Calcium