Protective effect of retinoid against endotoxin-induced mastitis in rats

A lipopolysaccharide (LPS) induced mastitis model in rats was used to study the protective effect of retinoid. Commencing at gestation day 10, retinoid (dissolved in olive oil) or an equal volume of olive oil was administered to rats daily by gavage until parturition. LPS or pyrogen-free physiological saline was inoculated into the mammary gland 72h after parturition and the rats were euthanized at 12h post-infection. Myeloperoxidase (MPO), N-acetyl -beta-D- glucosaminidase (NAGase), tumor necrosis factor-alpha (TNF-alpha), interleukin-8 (IL-8) in mammary tissues and CD4(+)/CD8(+) in peripheral blood were increased and serum MPO and IL-2 in mammary tissues were decreased 12h after LPS infusion. Retinoid decreased MPO, NAGase, and TNF-alpha in mammary tissue and increased IL-2 in serum. Four thousand and 8000 I.U/kgaEuro cent d of retinoid significantly decreased the infiltration of PMNs in mammary alveoli and ameliorated the imbalance of CD4+/CD8+ in peripheral blood. These results suggest that retinoid protected against LPS-induced mastitis in a rat model.