21. Histochemical distribution of NOS and 5'N in human glioblastoma

Nitric oxide (NO), formed from L-arginine by the enzyme nitric oxide synthase (NOS) and adenosine, produced by 5'nucleotidase (5'N) are implicated in several neurophysiological processes. In addition, 5'N is retained a linker protein involved in cell motility. Alteration of both enzyme activities seem to be responsible for some pathological states of the central nervous system (CNS). In the present study we have analysed the distribution of NOS (by means of NADPH-d histochemistry and NOS immunohistochemistry) and of 5'N in human glioblastoma samples. Both enzyme activities were observed in tumor specimens; moreover NADPH-d-positivity and NOS-immunoreactivity were often co-localized in the tumor cells. However, different patterns of reactivity were observed in different areas of the same sample, depending on the density, the distribution and the morphological aspect of the malignant cells. The findings were interpreted on the basis of the cytotoxic effects due to NO production by tumor cells, and on non-catalytic role of 5'N that acting as adhesive molecule can favour malignant cell invasion of normal brain.