Relation of catecholamines to collagen synthesis

Atherosclerosis. I. A leiomyoproliferative disease of the arteries resulting from breakdown of the endothelial barrier to potent blood growth factors. II. Perspectives in atheroprophylaxis

For a historical survey of the pathogenesis of atherosclerosis the reader is referred to references 1 and 2. Comprehension of the vessel-blood interface homeostasis hinges upon an understanding of the pathophysiology of angio-lymphoid relationships. Even in the smooth contact of the intact hydrophobic intimal lining with the marginal flow of the circulatory stream, small amounts of thrombin and small aggregates of aging platelets float by under physiologic conditions. Since endothelial cells of the vascular intima contain receptors for thrombin, filling these receptors with thrombin becomes a stimulus for the production of prostacyclin (PGI2) by the endothelial cells; PGI2 in turn inhibits adherence of the small platelet aggregates by ADP; homeostasis is maintained. The size of physiologic thrombin-producing platelet microaggregates is controlled by physiologic levels of antithrombin III.

Histochemical detection of monoamine oxidase activity in smooth muscle and epithelial tissues of Mytilus edulis L. and Mytilus galloprovincialis Lmk

Monoamine oxidase (MAO) activity was detected in the glio-interstitial tissue of the anterior byssus retractor muscle (ABRM) of Mytilus by the use of either dopamine or 5-HT as substrate and nitro blue tetrazolium salt as an electron receptor. Both substrates gave superimposable patterns. However, dopamine reactivity was very weak. Discrete but clear MAO activity was detected in the periphery of the smooth muscle cell, i.e., at the level of the peripherally localized mitochondria. The presence of MAO in the epithelium of the buccal palps was also demonstrated. These histochemical observations can be correlated with certain ultrastructural aspects, in particular the presence electron dense organelles profiles in glio-interstitial cells. This MAO activity is discussed in relationship with the high 5-HT content of ABRM and the control of its relaxation. Pigment formation and/or collagen tanning are discussed in terms of a possible relationship with inactivation of biogenic amines. These results complement previous data concerning the glio-interstitial tissue found in close association with muscle and nerve structures.