Einfluß der Vordehnung auf die Dynamik der glatten Gefäßmuskulatur

Summary

• 1. Isolated helical strips of rat aorta, splenic artery (hog) and coronary artery (hog and cattle) were stretched with various intensities. Determinations of the influence of this passive stretch on the efficiency of activation by potassium-depolarization, noradrenaline or angiotensin showed an increase of the induced contraction amplitude up to an initial stretch of more than 8000 dynes per mm² sectional area (Fig.2).

• 2. An augmentation of the initial stretch possibly depolarized the membrane and this caused a shift of the dose-response curve of potassium to lower concentrations (Fig.4).

• 3. The contraction amplitude of aorta or splenic artery induced by noradrenaline amounted to an average of 120% or of 111% of the value after potassium depolarization (Fig.1). The influence of the initial stretch on this relationship is only slight (Fig.3). The most effective concentration of noradrenaline was about 5 μg/ml; it was not possible to show a correlation between the initial stretch and the maximal effective dose of noradrenaline.

• 4. Noradrenaline distinctly relaxed the coronary arteries. The maximal effective dose for this reaction was also about 5 μg/ml (Fig.1).

• 5. Angiotensin caused a contraction in all investigated preparations (Fig.1) and became more effective after an increase of the initial stretch (Fig.3). There was no relationship between the degree of stretch and the most effective dose of angiotensin.

• 6. The amplitude of contraction was mainly influenced by the initial stretch and independent of the kind of activation (depolarization, noradrenaline, angiotensin). Therefore the stretch obviously affected later steps within the activation mechanism. This could be ascribed, for example, to an increase of the number of interaction sites of the contractile proteins caused by increased stretch.