Cytidine (5 ') diphosphocholine-induced decrease in cerebral platelet activating factor is due to inactivation of its synthesizing enzyme cholinephosphotransferase in aged rats

Levels of cerebral platelet activating factor (PAF) result from the balance between the activities of its synthesizing enzyme dithiothreitol (DTT)- in sensitive cholinephosphotransferase and its degradative enzyme PAF acetylhy drolase. Cerebral fractions of aged rats (19 months) displayed higher level s of PAF acetylhydrolase isoenzymes (P < 0.05; n = 4), unaltered levels of DTT-insensitive cholinephosphotransferase and lower PAF levels than young a nimals (2 months). Cerebral fractions of aged rats treated with cytidine (5 ') diphosphocholine displayed lower DTT-insensitive cholinephosphotransfera se (55% after 8 days of treatment with 350 mg/kg per day, P < 0.05; n = 4), unaltered levels of PAF acetylhydrolase and lower PAF levels than untreate d control animals. Thus our data would indicate that decrease of cerebral P AF may be attributed to an activation of PAF acetylhydrolase in ageing, and to an inactivation of DTT-insensitive cholinephosphotransferase in cytidin e (5') diphosphocholine treated animals. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.