Abstract
INTRODUCTION: The study was designed to investigate the effects of repeated lipopolysaccharide (LPS) treatment on growth performance, lymphoid organ indexes, and blood cells in Sprague-Dawley rats. MATERIAL AND METHODS: Forty healthy weaned Sprague-Dawley rats were randomly equally divided into LPS and control groups. Each rat in the LPS group was injected via the caudal vein with LPS (100 μg/kg b.w.) for 10 days, and the control group was treated with an equal volume of normal saline. On the 1(st), 4(th), 7(th), and 10(th) days, growth performance, lymphoid organ indexes, and blood cells were evaluated in five necropsied rats. RESULTS: When rats were treated 3-10 times with LPS, their body weight and average daily gains increased more slowly than in the control group (P < 0.05). Repeated LPS treatment significantly increased spleen weight and the ratio of spleen to body weight (P < 0.05). White blood cells, neutrophils, and neutrophil percentage increased (P < 0.05) remarkably, but lymphocyte percentage, haemoglobin, and blood platelet counts decreased significantly (P < 0.05). CONCLUSION: LPS treatment obviously suppresses growth and promotes peripheral immune organ proliferation. It is indicated that host protective mechanism can be activated by multiple small doses of LPS and prevents organs from further damage during stress status.