Abstract
Monoamine oxidase (MAO) activity in sera from patients with various pneumoconioses including asbestosis, silicosis, talcosis, graphitosis and arch welder's pneumoconiosis was estimated. This enzyme was also determined in other diseases such as liver cirrhosis, congenital heart disease and pulmonary tuberculosis for comparison. The total number of cases was 105, and the following results were obtained.
1) Serum MAO activity in pneumoconioses seemed to show high levels with the degree of diffuse or nodular fibrosis in lungs, which was assessed by roentgenographic manifestations. This enzyme in liver cirrhosis and congenital heart disease revealed also high value as in pneumoconiosis.
2) However MAO activity in sera from patients with pulmonary tuberculosis or silicosis, associated with tuberculosis who were given orally isoniazid (INH) was extremely inhibited and lowered until 4 weeks after INH discontinuation.
3) Since MAO is reported to be copper-pyridoxal phosphate dependent enzyme in beef serum, pyridoxal phosphate with the dosis of 60mg daily was administered to those patients with tuberculosis for 2 weeks. But this enzyme in their sera remained inactivated.
4) Mitochondrial MAO activity in tissues from a patient with asbestosis was measured. The activity of this enzyme in lungs revealed 22.3, while those in aorta and liver were 28.4 and 12.0mμmole/hr/mg protein respectively.
