title: 24-hour pattern of circulating prolactin and growth hormone levels and submaxillary lymph node immune responses in growing male rats subjected to social isolation.
abstract: To assess the effect of social isolation of growing rats on 24-h rhythmicity of circulating prolactin and growth hormone (GH) levels and submaxillary lymph node immune responses, male Wistar rats were either individually caged or kept in groups (4-5 animals per cage) for 30 d starting on d 35 of life. Plasma prolactin and GH levels, and submaxillary lymph node lymphocyte subset populations, interferon (IFN)-gamma release and mitogenic responses to concanavalin A (Con A) and lipopolysaccharide (LPS) were determined at six time intervals during the 24 h span. Social isolation brought about changes in mean values and 24-h pattern of plasma prolactin and GH levels and lymph node immune responses. After isolation, prolactin and GH mean values decreased, and lymph node T, B, non T-non B, CD8+, and CD4+-CD8+ cells augmented, whereas lymph node CD4+/CD8+ ratio, IFN-gamma release and mitogenic responses decreased. Social isolation resulted in disruption of 24 h rhythmicity of every immune parameter tested. CD4+/CD8+ ratio, IFN-gamma release and Concanavalin A (Con A) and lipopolysaccharide (LPS) responses correlated significantly with plasma prolactin or GH levels while T/B ratio correlated with plasma prolactin levels only. B, non T-non B, and CD4+-CD8+ cells correlated negatively with plasma prolactin. Modifications in mean value and 24-h rhythmicity of plasma prolactin and GH levels are presumably involved in the effect of social isolation on immune responsiveness.
authors.affiliation: Departamento de Bioquímica y Biología Molecular III, Facultad de Medicina, Universidad Complutense, 28040 Madrid, Spain. pelayos@med.ucm.es
authors.forename: Ana I
authors.initials: AI
authors.lastname: Esquifino
authors.forename: María P
authors.initials: MP
authors.lastname: Alvarez
authors.forename: Pilar
authors.initials: P
authors.lastname: Cano
authors.forename: Fernando
authors.initials: F
authors.lastname: Chacon
authors.forename: Carlos F
authors.initials: CF
authors.lastname: Reyes Toso
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Cardinali
mesh_terms: D000818:Animals; D000917:Antibody Formation / Q000187:drug effects; D016516:CD4-CD8 Ratio; D002940:Circadian Rhythm; D003208:Concanavalin A / Q000494:pharmacology; D013006:Growth Hormone / Q000097:blood*; D007371:Interferon-gamma / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008198:Lymph Nodes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D016131:Lymphocyte Subsets / Q000166:cytology; D008297:Male; D008938:Mitosis; D011388:Prolactin / Q000097:blood*; D051381:Rats; D017208:Rats, Wistar; D012934:Social Isolation; D013363:Submandibular Gland
chemical_list: D008070:Lipopolysaccharides; D003208:Concanavalin A; D007371:Interferon-gamma; D011388:Prolactin; D013006:Growth Hormone