Jul 30, 1976

Force velocity relations in vascular smooth muscle: the influence of pH, pCa, and noradrenaline

Pflügers Archiv : European journal of physiology
U PeiperR Laven


The kinetics of vascular smooth musclw activity was studied by means of afterloaded isotonic contractions of the tetanized rat portal vein at varied pH (8.0-5.9), pCa (3.4-2.1), and during noradrenaline incubation (0.4 mug/ml). Under control conditions (pH 7.3, pCa 2.6) the following parameters of the force velocity relation were calculated: a of Hill's equation (relating to the isometric peak tension) = 0.36; b (relating to the actual muscle length) = 0.19 ML/s; VM Trelating to the actual muscle length) = 0.56 ML/s. Within the range of pCa between 2.0 and 3.2 the amount of force generation (= delta P) depended on the extracellular calcium level whereas the extrapolated velocity of shortening of the unloaded preparation (= VM) did not. Also pH changes between 8.0 and 6.8 as well as noradrenaline incubation at a pH of 5.9 affected delta P quite considerably, but VM only scarcely. At a pH of 6.3, however, VM was distinctly diminished, and a reduced calcium sensitivity of the ATPase was inferred from the shift of ED50 of extracellular calcium from 0.66 mM Ca at a pH of 7.3 to 1.56 mM Ca at a pH of 6.3 (P less than 0.0005). It is concluded from these results that the experimental conditions-pCa between 2.0 and 3.2, pH between 8.0 a...Continue Reading

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Mentioned in this Paper

Blood Vessel
Portal Vein Structure
Smooth Muscle
Norepinephrine, (+, -)-Isomer
Hydrogen-Ion Concentration
Rats, Laboratory

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