AMP deaminase in rat brain: Localization in neurons and ependymal cells

The purine nucleotide cycle enzyme AMP deaminase (AMPD) catalyzes the irrev ersible hydrolytic deamination of AMP. The physiological function of the pu rine nucleotide cycle in the brain is unknown. In situ hybridization and im munocytochemical studies were performed to identify the regional and cellul ar expression of AMPD in rat brain with the goal of elucidating the neural function of the purine nucleotide cycle. AMPD messenger RNA was detected in ventricular ependymal cells and cells of the choroid plexus and in neurons of distinct brain areas. Although only low antibody titers were obtained b y immunization with the purified sheep brain AMPD, immunization of mice wit h synthetic lipopeptide vaccines containing oligopeptides derived from a kn own partial complementary DNA sequence of the enzyme yielded an antiserum s uitable for immunocytochemistry. Immunostaining of cells in culture showed that neurons but not astroglial cells express appreciable amounts of the en zyme. Results of immunocytochemical staining performed on rat brain slices were in accord with the localization of AMPD messenger RNA, thus confirming the expression of AMPD in neurons of the brain stem, hippocampus, cerebell ar nuclei and mesencephalic nuclei, as well as in ventricular ependymal cel ls and their cilia. (C) 2001 Wiley-Liss, Inc.