Benzylamine oxidase activity in pathological states

Benzylamine oxidase (BzAO) is an amine oxidase of unknown physiological significance. However, clinical studies show that BzAO activity is elevated in the serum of patients with fibrotic disorders and during growth spurts in children. Some workers have suggested, therefore, a functional association of BzAO in the biochemistry of connective tissue. The objective of the present research was to test this proposed association by measuring BzAO activity in conditions exhibiting enhanced connective tissue growth and proliferation. BzAO activity was measured in cellular systems as well as in serum, utilizing both human and animal tissues (human atherosclerotic aortae, bleomycin-induced lung fibrosis in rats, spontaneously hypertensive rats, and the hormonally manipulated rat uterus). No specific relationship between the activity of BzAO and connective tissue growth was found. BzAO activity was decreased significantly in plaque regions of atherosclerotic aortae, but this decrease was due to a reduced cell population density compared with nonplaque areas and normal aortae. In bleomycin-treated lungs, lysyl oxidase activity increased markedly, but again BzAO activity showed no specific change (lung and serum). Overall, similar negative results were found in hypertensive rats and in the rat uterus. In rat uteri (ovariecto-mized and estrogen-treated), BzAO activity was found to follow passively organ weight changes and, unlike monoamine oxidase, was unresponsive to direct hormonal influences. Since BzAO may be located predominantly in association with the smooth muscle cells of uterine blood vessels, changes in the activity of uterine BzAO may reflect changes in the vascularity of this organ (number of blood vessels per unit weight or wall thickness or both). An organ specific, disease dependent change in BzAO activity was found in diabetic rats where the activity of the serum and kidney enzyme was elevated in association with hyperglycemia. BzAO activity of lung, aorta and pancreas did not change significantly. Studies showed a different substrate profile for BzAO in the serum and kidney from that in aorta, lung and pancreas, indicating a possible heterogeneity of BzAO activity. It is speculated that elevations in the activity of serum BzAO may be reflective of renovascular damage associated with diabetes mellitus.