| IntroductionProlactin (PRL) is an important endocrine hormone released by the antierior pituitary with immunoregulatory potential. It appears to play a role in stimulating activity of a number of autoimmune diseases, and hyperprolactinemia has been reported in patients with RA.The rat model of adjuvant arthritis ( AA) is the first selection for human rheumatoid arthritis ( RA) study. Berczi et al have indicated PRL is necessary for the development of AA. Sex hormones are involved in the autoimmune diseases. Female AA rats are more prone to arthritic inflammation than male rats. In order to determine the roles of PRL and sex hormones in the development of AA, we compared the rates of foot swelling in female AA rats ( FEMALE/AA) ovariecto-mized female AA rats (OVX/AA) and male AA rats (MALE/AA) , and we also determined whether lymphocytes response from AA rats is altered by PRL in vitro.Methods1. Measurement of the rates of foot swelling in AA rats Adjuvant arthritis was induced in female rats, male rats, and ovariectomized female rats by injecting their left hind paw with 0.1ml Freud's complete adjuvant (CFA). After injection, we measured thevolumes of foot swelling in A A rats every 4 days.2. Measurement of splenocytes proliferationOVX/AA rats and MALE/AA rats were killed after 28 days, the spleen was removed aseptically, placed in hanks ( pH = 7. 2). Splenocytes were suspended at 2 x 106 ml in RPME - 1640 medium in 96 -well tissue culture plates. 100μl splenocytes were incubated with 100μl various concentrations of concanavalin A (ConA, 5|xg/ml) or rat PRL (0. 5μg /ml) according to groups. After incubation for 48h, 10μl MTT was added to each well, and 4h later, 100 μl DMSO was added and cell proliferation was measured using MTT assay.3. IL ?2 assay(1) Induction of IL - 2 : After a 24h incubation with PRL, ConA or medium alone, lymphocytes were removed by centrifugation, and the culture medium was collected and stored frozen at - 20 ℃.(2 ) Preparation of effect cells; spleen single ?suspensions were prepared and ConA was added. Cells were collected after 48h and washed twice with hanks. Then cells were suspended in complete culture medium.(3) Measurement of IL -2: 100μl supernatants with IL -2 and 100μl effect cells were added to 96 - well tissue culture plates. IL -2 activity was assayed on IL ?2 dependent effect cells. Human recombi-nant IL - 2 was served as the standard.Results1. In left and right foots, the rates of foot swelling in OVX/AA rats is significantly higher than FEMALE/A A rats ( p < 0. 05). FEMALE/AA rats is significantly higher than MALE/AA rats (p < 0.05).2. Our study demonstrated ConA - stimulated splenocytes proliferation and IL -2 production in AA rats is lower than controls (p <0. 01). PRL could promote splenic lymphocytes proliferation and IL-2 production in OVX/AA rats, but PRL had no effect on those of MALE/AA.DiscussionWhat is the role of estrogen in the development of AA? In our experiment, in order to remove the influence of estrogen, AA was induced in OVX female rats, female rats and male rats. Our study finds the rates of foot swelling in OVX/AA is higher than those of FEMALE/AA, FEMALE/AA is higher than those of MALE/AA. Our results indicated: 1) estrogen has an inhibitory effect on the development of AA. As noted in the previous sections, estrogen is biphasic, as estrogen appears to suppress T cell - mediated autoimmune diseases and to promote immune complex - mediated process. A A is considered to be a T cell - mediated autoimmune disease. 2) Both estrogen and androgen have inhibitory effect in AA, but the function of androgen is more important.Our results also find that ConA - stimulated splenocytes proliferation and IL-2 production are lower in AA rats than those of controls. This phenomenon cannot be explained till today. We considered it is maybe due to the existence of special anti - T cell antibody in the serum of A A rats.As noted, PRL has stimulatory effect on the autoimmune diseases thro...
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