Elevated activity of semicarbazide-sensitive amine oxidase in blood from patients with skeletal metastases of prostate cancer

The semicarbazide-sensitive amine oxidases constitute a group of copper-con taining enzymes whose physiological function is unclear. The enzymes are pr esent in various tissues, including blood plasma. At present, the source of the plasma enzyme in humans is not known. Results of a recent study sugges ted that semicarbazide-sensitive amine oxidase is expressed in the skeleton , e.g. in the spine. Using an indirect autoradiographic method in mice, we provide evidence that semicarbazide-sensitive amine oxidase is present in h igh abundance in bone tissue. Specific activities of semicarbazide-sensitiv e amine oxidase were estimated in blood samples from subjects with femoral bone fractures. Moreover, enzyme activities were also measured in patients suffering from prostate cancer with skeletal metastases. The level of speci fic semicarbazide-sensitive amine oxidase activity in serum was significant ly elevated in patients with skeletal metastases compared with both healthy controls and patients having prostate cancer without signs of skeletal met astases. Based on the results of the present study, we propose that semicar bazide-sensitive amine oxidase in blood plasma may originate, at least in p art, from the skeleton.