5-nucleotidase activity in aortas of arteriosclerotic breeder rats

Abstract

The activity of the enzyme, 5-nucleotidase was measured, chemically and histochemically, in the aortas of male and female control rats, free of arterial disease, as well as male and female breeder rats which develop microscopic and grossly-visible arteriosclerosis of the aorta, respectively. Female rats manifested much greater aortic 5-nucleotidase activity than male rats. Very little difference could be detected between the aortic enzyme activity of male control rats and male breeder rats which had aortic microscopic lesions only. However, there was a significant and progressive increase in aortic 5-nucleotidase activity commensurate with and paralleling the progression of the severity of arteriosclerosis as well as its anatomical spread from the abdominal aortic segment to the arch and lastly, the thoracic aortic segment. The histochemical tests demonstrated that 5-nucleotidase activity first appears in the tunica intima coincidental with the appearance and accumulation of mucopolysaccharide. As the intimal mucopolysaccharide is converted into collagen the 5-nucleotidase activity disappears. In the media, 5-nucleotidase activity becomes diffusely and strongly positive in close proximity to the internal elastic membrane. As the medial degenerative changes become more exacerbated and calcific changes appear the 5-nucleotidase reaction becomes most intense. These chemical and histochemical observations are construed to be an indication of the hormonal effects of repeated breeding inducing medial smooth muscle cell changes in association with 5-nucleotidase activity to affect ground substance and connective tissue changes which favor sclerosis and calcification of the aortic wall of breeder rats.