Inflammatory responses to carrageenan injection in LEW/N and F344/N rats: LEW/N rats show sex- and age-dependent changes in inflammatory reactions.
We studied the inflammatory responses of LEW/N and F344/N inbred rat strains after peripheral injection of carrageenan. The inflammatory responses were assessed in terms of volume, relative and total white blood cell counts of the exudates. Moreover, in both strains, blood CD4, CD8, CD25, naive CD4 (CD4/CD45RC) cell and B (CD45R) cell counts and plasma corticosterone levels, constituents of systemic inflammatory responses to carrageenan were evaluated. In general, LEW/N rats are highly responsive to challenge with carrageenan, whereas F344 rats are not. The strong local inflammatory responses to carrageenan are primarily exhibited by female LEW/N rats. The intensity of local inflammatory responses of LEW/N rats changes with the rat age, the highest exhibited by LEW/N rats up to 3 months of age, thereafter the carrageenan-induced inflammatory responses decline. Our results indicate that peripheral injection of carrageenan induces strong systemic immune component. After carrageenan injection, increases in CD8 and naive CD4 blood lymphocytes are seen. Although the carrageenan challenge does not change CD4 blood lymphocytes in both LEW/N and F344/N rat strains, LEW/N rats exhibit higher levels of CD4 cells than F344/N rats. Additionally, LEW/N rats demonstrated lower levels of B cells and higher naive CD4 lymphocytes. Carrageenan challenges induce significant increases in plasma corticosterone response in F344/N rats, as well as increases in LEW/N rats 1 h after injection. Our data stress the importance of rat age and gender in experiments studying inflammatory responses.
Misiewicz
B
B
Clinical Neuroendocrinology Branch, National Institute of Mental Health, Bethesda, MD 20892, USA.
Zelazowska
E
E
Raybourne
R B
RB
Cizza
G
G
Sternberg
E M
EM
D000367:Age Factors; D000818:Animals; D002351:Carrageenan / Q000633:toxicity*; D003345:Corticosterone / Q000097:blood; D005260:Female; D007249:Inflammation / Q000139:chemically induced* / Q000276:immunology / Q000503:physiopathology; D007279:Injections, Subcutaneous; D018655:Lymphocyte Count; D016131:Lymphocyte Subsets; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D011917:Rats, Inbred Lew
D002351:Carrageenan; D003345:Corticosterone