ISSN:
1432-2013
Keywords:
Smooth muscle
;
Force-velocity relation
;
Ca2+, Mg2+
;
Calmodulin
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Rat portal veins were chemically skinned using Triton X-100 and mounted for isometric and quick release experiments at 20°C. The skinned preparations were activated by Ca2+ (EGTA-buffered) in solutions containing 2 mM free-Mg2+ and 1 μM calmodulin. Half maximal isometric force was obtained at pCa=6.2. Maximal force of the skinned preparations, at pCa=4.5, was 8.2±0.8 mN/mm2 (n=6). Force-velocity relations were determined at varied Ca2+-concentrations. Maximal shortening velocity (V max) was 0.10±0.01 lengths/s at pCa=4.5. At decreasing Ca2+-levelsV max decreased (at pCa=6.25,V max=0.05 l/s). At pCa =9 an increased level of free-Mg2+ (15mM) induces a slow and submaximal increase in tension. Force velocity relations of Mg2+-induced contractures were not different from those of Ca2+-contractures of similar magnitude (pCa=6.3). The results indicate that the degree of activation of the contractile system, as regulated by Ca2+ and Mg2+, influences the kinetic properties of the actomyosin interaction as well as the force development.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00585160
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