A note on the actomyosin content of the arterial wall

Differences were found between various parts of the aorta, the actomyosin increasing with increasing distance from the heart, and the inhibition of the former by salyrgan is probably the only practicable means for the evaluation of actomyOSin in arterial wall.

Abstract

The possibilities of a chemical determination of actomyosin as a measure of the amount of smooth muscle in the arterial wall were followed up. As the basis the ATPase activity of actomyosin was used. The arterial wall contains considerable ATPase activity, a relatively small proportion of which can be ascribed to actomyosin. The bulk of the activity is associated with proteins soluble at low ionic strength. Actomyosin preparations from the arterial wall, obtained by precipitation with water or by dialysis, contain—together with actomyosin—some other ATPases, probably originating from microsomes and granula. As a specific means of determination of actomyosin ATPase in the presence of other ATPases the inhibition of the former by salyrgan was investigated. This kind of inhibition is probably the only practicable means (applicable to arterial extracts without preliminary separation of actomyosin) for the evaluation of actomyosin in arterial wall. The method has been tested on various arterial samples. Species differences were observed in the content of actomyosin between human aorta and bovine or pig aorta. A noteworthy difference between calf aorta and the aorta of mature cattle was found. Differences were found between various parts of the aorta, the actomyosin increasing with increasing distance from the heart.