Biomaterial Database

Role of myosin light-chain phosphorylation in guinea pig gallbladder smooth muscle contraction. 1994

R J Washabau, and M B Wang, and C Dorst, and J P Ryan

Department of Clinical Studies, University of Pennsylvania School of Veterinary Medicine, Philadelphia.

In acetylcholine (ACh)-stimulated gallbladder smooth muscle, we have previously shown that phosphorylation of the 20,000-Da myosin light chains is necessary for the initiation of contraction, that myosin is stably phosphorylated at steady state, and that dephosphorylation of cross bridges is not necessary for the slowing of cross-bridge cycling rates during the period of steady-state isometric stress. The present studies were undertaken to determine whether 1) K+ (60 or 80 mM) or cholecystokinin (CCK, 10(-8) M) stimulation is accompanied by changes in myosin light-chain phosphorylation in gallbladder smooth muscle and 2) dephosphorylated noncycling cross bridges exist in K(+)- or CCK-stimulated gallbladder smooth muscle. Isometric stress, isotonic shortening velocity, and myosin light-chain phosphorylation were determined during contraction with K+ or CCK. Steady-state isometric stress was reached within 2.5 min of stimulation with K+ or CCK and was maintained for the duration of the stimulation. Stimulation with K+ or CCK was associated with rapid increases in myosin light-chain phosphorylation and maintenance of myosin light-chain phosphorylation during the stimulation. In contrast, isotonic shortening velocity was maximal at 1 min of stimulation with either K+ or CCK and then declined significantly to values that were only 26-32% of the peak velocity. These data, along with data from previous experiments with ACh, suggest that myosin light-chain phosphorylation is essential in the initiation of contraction in gallbladder smooth muscle, regardless of the source of Ca2+ or of the contractile agonist.(ABSTRACT TRUNCATED AT 250 WORDS)

UI	MeSH Term	Description	Entries
D007537	Isometric Contraction	Muscular contractions characterized by increase in tension without change in length.	Contraction, Isometric,Contractions, Isometric,Isometric Contractions
D009119	Muscle Contraction	A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.	Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D009130	Muscle, Smooth	Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)	Muscle, Involuntary,Smooth Muscle,Involuntary Muscle,Involuntary Muscles,Muscles, Involuntary,Muscles, Smooth,Smooth Muscles
D009218	Myosins	A diverse superfamily of proteins that function as translocating proteins. They share the common characteristics of being able to bind ACTINS and hydrolyze MgATP. Myosins generally consist of heavy chains which are involved in locomotion, and light chains which are involved in regulation. Within the structure of myosin heavy chain are three domains: the head, the neck and the tail. The head region of the heavy chain contains the actin binding domain and MgATPase domain which provides energy for locomotion. The neck region is involved in binding the light-chains. The tail region provides the anchoring point that maintains the position of the heavy chain. The superfamily of myosins is organized into structural classes based upon the type and arrangement of the subunits they contain.	Myosin ATPase,ATPase, Actin-Activated,ATPase, Actomyosin,ATPase, Myosin,Actin-Activated ATPase,Actomyosin ATPase,Actomyosin Adenosinetriphosphatase,Adenosine Triphosphatase, Myosin,Adenosinetriphosphatase, Actomyosin,Adenosinetriphosphatase, Myosin,Myosin,Myosin Adenosinetriphosphatase,ATPase, Actin Activated,Actin Activated ATPase,Myosin Adenosine Triphosphatase
D010766	Phosphorylation	The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.	Phosphorylations
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D005260	Female		Females
D005704	Gallbladder	A storage reservoir for BILE secretion. Gallbladder allows the delivery of bile acids at a high concentration and in a controlled manner, via the CYSTIC DUCT to the DUODENUM, for degradation of dietary lipid.	Gallbladders
D006168	Guinea Pigs	A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.	Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D006706	Homeostasis	The processes whereby the internal environment of an organism tends to remain balanced and stable.	Autoregulation