| Autor: |
Peiper, U., Ehl, M., Johnson, U., Laven, R. |
| Zdroj: |
Pflügers Archiv: European Journal of Physiology; 1976, Vol. 364 Issue 2, p135-141, 7p |
| Abstrakt: |
The kinetics of vascular smooth muscle 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 μg/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; V (relating 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 (=Δ P) depended on the extracellular calcium level whereas the extrapolated velocity of shortening of the unloaded preparation (= V) did not. Also pH changes between 8.0 and 6.8 as well as noradrenaline incubation at a pH of 5.9 affected ΔP quite considerably, but V only scarcely. At a pH of 6.3, however, V was distinctly diminished, and a reduced calcium sensitivity of the ATPase was inferred from the shift of ED 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<0.0005). It is concluded from these results that the experimental conditions-pCa between 2.0 and 3.2, pH between 8.0 and 6.8, and noradrenaline added at a pH of 5.9-obviously change the intracellular calcium concentration which influences the number of activated interaction sites rather than the velocity of crossbridge movement. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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