1. An attempt was made to clarify the role of NaCl for the induction of hypertension via the effeet of NaCl on the contraction and relaxation mechanism of the arterial wall with use of myosin B and microsomal fraction prepared from the bovine carotid artery. 2. The microsomal fraction was capable of taking up calcium in the presence of Mg
++ and ATP, but the capacity was very weak and very low. 3. The microsomal fraction also inhibited the superprecipitation of arterial myosin B in a slight degree. The further study is required in order to clarify the exact mechanism. 4. Elevation of the ratio of NaCl to KCl in a reaction mixture led to enhance the super-precipitation of arterial myosin B with or without the microsomal fraction. This finding might lead to on assumption that the elevation of the ratio of NaCl to KCl in arterial smooth muscle enhanced the contraction of the arterial wall, resulting in an increase of peripheral arterial resistance followed by high blood pressure.
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