Suppression of adjuvant arthritis in rats with chronic bromocriptine treatment does not prevent associated oxidative stress.

Abstract

We studied the effect of prolactin (PRL) inhibition by bromocriptine (BRC) in the first phase of adjuvant induced arthritis (AA), up to day 11(BRCl-AA), and in the whole time course of AA, up to day 23 (BRC-AA), on the development of the disease in male Lewis rats. On day 24, arthritic rats showed inhibition of PRL secretion, but not PRL mRNA expression in adenopituitaries. BRC treatment suppressed PRL serum levels and PRL mRNA expression in adenopituitaries. In BRC/-AA group PRL levels and PRLmRNA were at the level of rats with AA. Serum corticosterone (CORT) was stimulated by AA from 16.9+/-5.8 to 59.1+/-8.7 ngml(-1), p<0.05, to the same level in BRC-control (BRC-C) and BRC-AA group and further potentiated in BRCI-AA group (148.2+/-33.1 ngml(-1), p<0.05 vs. group with AA). Hind paw swelling was reduced but not completely inhibited in BRC1-AA group and totally prevented in BRC-AA rats as was the core temperature (36.5+/-0.1 degrees C vs. 37.4+/-.0.1 degrees C in AA rats on day 23, p<0.01). Serum concentration of NO-ZNO-3 rose in rats with AA to 28.7+/-2.5 &mgr;mo1L-1 against. 13.9+/-1.9 &mgr;molL(-1) in controls (p<0.01), remained elevated in BRC-AA group and was potentiated in BRC1-AA group (48.2+/-3.5 &mgr;mol(-1), p<0.01 vs. AA or BRC1-AA group) Thiobarbituric acid reactive substances (TBARS) and antioxidant capacity in the spleen were enhanced in rats with AA and to the same extent in BRC-AA or BRC1-AA groups. These results show a discrepancy between the suppression of clinical symptoms and persisting oxidative stress in AA rats after the BRC induced PRL inhibition. The potentiation of nintric oxide (NO-) production after the sudden cessation of PRL inhibition during the disease may promote further joint damage.