REGULATION of the CYCLIC GUANOSINE 3′-5′ MONOPHOSPHATE SYSTEM IN HUMAN BRAIN TUMORS

Abstract
Several reports suggested that cyclic[c]GMP and cAMP are involved in the regulation of cellular proliferation. Following previous reports on the cAMP system in human brain tumors, the cGMP system was studied in the same pathological tissues by studying the activity of guanylate cyclase and cGMP phosphodiesterase (cGMP-PDE). The activity of both enzymes was lower in neurinomas and glioblastomas than in meningiomas or normal cerebral cortex. The subcellular distribution of guanylate cyclase in human cerebral cortex differed from that of neurinomas and glioblastomas. On the basis of such observations, the possibility that the regulatory mechanism of enzymes related to cyclic nucleotide metabolism is altered in brain tumors was discussed.