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At least 1,297 records · Page 72Linked to original sources
PubMed1989

Smooth muscle contraction and local anesthetics: calmodulin-dependent myosin light-chain kinase.

Myocardial depressant action of local anesthetics at toxic concentrations is well documented. Their effect on vascular smooth muscle, however, remains controversial. This study analyzed local anesthetic action on the subcellular smooth-muscle contractile system. Highly purified smooth-muscle myosin and myosin light-chain kinase (MLCK) were prepared from fresh turkey gizzards, and the phosphorylation of the myosin light-chain in the presence of Ca++ and calmodulin was evaluated by the urea gel-electrophoresis. Tetracaine 1.3.10(-3) M and bupivacaine 7.5.10(-3) M inhibited the MLCK 50%, whereas lidocaine 2.5.10(-2) M inhibited the MLCK 40%. The inhibitory action was partially reversed by increasing the calcium ion concentration from 1.10(-5) to 2.10(-4) M. On the other hand, raising the calmodulin concentration from 1.10(-7) M to 6.10(-7) M completely reversed the inhibition. A possible cause of the discrepancy in the anesthetic concentrations between subcellular and in vivo studies is discussed.

Bupivacaine↗
PubMed2000

Kavain inhibits murine airway smooth muscle contraction.

This study examined the effect of kavain, the principle biologically active component of kava, on murine airway smooth muscle. In isolated isometrically contracted tracheal ring preparations, kavain was noted to diminish the maximal contractile response to both muscarinic receptor activation and voltage-operated calcium channel activation. The IC50 for kavain in rings precontracted with carbachol was found to be 177 microM +/- 53.1, and, in rings precontracted with KCl, it was found to be 59.6 microM +/- 10.1. In addition, pretreatment with kavain attenuated airway smooth muscle contraction evoked with either carbachol or KCl. The EC50 for KCl was not affected by kavain pretreatment. However, the EC50 for carbachol was significantly affected by a high kavain pretreatment dose. Nitric oxide mediated relaxation was not observed to play a role in kavain's smooth muscle relaxing properties. Similarly, prostaglandin pathways are not likely involved in these effects since pretreatment of tracheal rings with indomethacin before carbachol contraction did not reduce the relaxant effect of kavain. The mechanism of kavain-induced relaxation and inhibition of contraction is likely due to a mechanism common to both contractile agonists that were employed in our study.

Animals↗
PubMed2002

HSP27 phosphorylation and interaction with actin-myosin in smooth muscle contraction.

We have investigated the role of heat shock protein 27 (HSP27) phosphorylation and the association of HSP27 with contractile proteins actin, myosin, and tropomyosin. Smooth muscle cells were labeled with [(32)P]orthophosphate. C2-ceramide (0.1 microM), an activator of protein kinase C (PKC), induced a sustained increase in HSP27 phosphorylation that was inhibited by calphostin C. C2-ceramide-induced (0.1 microM) sustained colonic smooth muscle cell contraction was accompanied by significant increases in the association of HSP27 with tropomyosin and in the association of HSP27 with actin. The significant increases occurred at 30 s after stimulation and were sustained at 4 min. Contraction was also associated with strong colocalization of HSP27 with tropomyosin and with actin as observed after immunofluorescent labeling of tropomyosin, actin, and HSP27 followed by confocal microscopy. Transfection of smooth muscle cells with HSP27 phosphorylation mutants indicated that phosphorylation of HSP27 could affect myosin association with actin. In conclusion 1) HSP27 phosphorylation appears to be necessary for reorganization of HSP27 inside the cell and seems to be directly correlated with the PKC signal transduction pathway, and 2) agonist-induced phosphorylation of HSP27 modulates actin-myosin interaction through thin-filament regulation of tropomyosin.

Actins↗
PubMed1991

Nonuniform volume changes during muscle contraction.

We measured dynamic changes in volume during contraction of live, intact frog skeletal muscle fibers through a high-speed, intensified, digital-imaging microscope. Optical cross-sections along the axis of resting cells were scanned and compared with sections during the plateau of isometric tetanic contractions. Contraction caused an increase in volume of the central third of a cell when axial force was maximum and constant and the central segment was stationary or lengthened slightly. But changes were unequal along a cell and not predicted by a cell's resting area or shape (circularity). Rapid local adjustments in the cytoskeletal evidently keep forces in equilibrium during contraction of living skeletal muscle. These results also show that optical signals may be distorted by nonuniform volume changes during contraction.

Animals↗