title: Diurnal rhythms in ornithine decarboxylase activity and norepinephrine and acetylcholine synthesis in submaxillary lymph nodes and spleen of young and aged rats during Freund's adjuvant-induced arthritis.
abstract: Aging has been associated with attenuation of amplitude and changes in period of many circadian rhythms. The present study was carried out to examine, in young (50 days old) and old (18 months old) rats, whether 24-h rhythms of cell proliferation (as assessed by measuring ornithine decarboxylase activity) and of presynaptic adrenergic and cholinergic markers change in lymph nodes and spleen during Freund's adjuvant-induced arthritis. Groups of young and old Sprague-Dawley rats were studied the day before, and on days 6, 12 and 18 after Freund's adjuvant injection. On day 16 after adjuvant injection, inflammation of hind paws, mainly in the ankle joints, was less marked in old than in young rats. Lymph node and splenic ornithine decarboxylase activity exhibited significant 24-h variations with maximal activity during daily hours. Before treatment, enzyme activity values were significantly lower in old rats in both tissues examined. During the immune reaction, lymph node and splenic ornithine decarboxylase augmented 8-10-fold, with progressively smaller amplitude of daily variations as arthritis developed. In every case, mesor and amplitude of ornithine decarboxylase activity were lowest in old rats. Submaxillary lymph node and splenic tyrosine hydroxylase activity attained maximal values at night. At every time interval after mycobacterium adjuvant injection, amplitude and mesor of tyrosine hydroxylase activity rhythm were lowest in old rats. A maximum in submaxillary lymph node 3H-acetylcholine synthesis occurred at the afternoon. On day 6 and 12 after Freund's adjuvant injection, lymph node 3H-acetylcholine synthesis was significantly smaller in old rats. Day-night differences in submaxillary lymph node or splenic ornithine decarboxylase and tyrosine hydroxylase activities, or in submaxillary lymph node 3H-acetylcholine synthesis, of rats treated with the adjuvant's vehicle, did not differ significantly from those seen in untreated controls. The results are compatible with an age-dependent decline of immune-mediated inflammatory responses. The activity of the central circadian oscillator, driven to the organs in part via the autonomic nervous system, seems also to deteriorate during aging.
authors.affiliation: Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, CC 243, 1425 Buenos Aires, Argentina. cardinal@mail.retina.ar
authors.forename: D P
authors.initials: DP
authors.lastname: Cardinali
authors.forename: L I
authors.initials: LI
authors.lastname: Brusco
authors.forename: L
authors.initials: L
authors.lastname: Selgas
authors.forename: A I
authors.initials: AI
authors.lastname: Esquifino
mesh_terms: D000109:Acetylcholine / Q000096:biosynthesis*; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001169:Arthritis, Experimental / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D008198:Lymph Nodes / Q000378:metabolism; D008221:Lymphoid Tissue / Q000378:metabolism*; D008297:Male; D008437:Maxilla; D009638:Norepinephrine / Q000096:biosynthesis*; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013154:Spleen / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D014446:Tyrosine 3-Monooxygenase; D009955:Ornithine Decarboxylase; D000109:Acetylcholine; D009638:Norepinephrine