Oil-induced arthritis in DA rats: tissue distribution of arthritogenic 14C-labelled hexadecane

As part of the study of the pathogenesis of oil-induced arthritis in DA rats, the tissue dissemination of arthritogenic oil labelled with 14C has been determined. Rats received labelled hexadecane in arthritogenic doses by the intradermal route and were killed at 1 and 6 h, 2, 10, 14, 18 and 27 days after injection. Whole-body autoradiography was performed and localization of radioactivity in different organs was investigated. With the exception of the injection site, the lymph nodes showed the highest content of radioactivity throughout the study. Radioactivity could be seen in the popliteal, inguinal and axillary lymph nodes. Detailed examination of lymph nodes revealed at 1 h radioactivity in the subcapsular sinus of the lymph node. By 10 days the activity had spread to the cortex and paracortex, apart from the subcapsular sinus. The activity in other lymphoid organs, such as the bone marrow and spleen, was more transient, with a peak at 2 days. Oil disseminating to joints was not prominent: very little radioactivity was observed in the knee joints of both non-arthritic and arthritic animals. From these data it is suggested that the adjuvant oil exerts its major proarthritogenic activity in the lymph nodes rather than directly in the joints.