Effects of Repeated Lipopolysaccharide Treatment on Growth Performance, Immune Organ Index, and Blood Parameters of Sprague-Dawley Rats

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.

Keywords: blood cells; growth performance; immune organ index; lipopolysaccharide; rat.

Fig. 1

Effects of LPS treatments on the growth performance of SD rats (* P < 0.05, ** P < 0.01). A – body weight, B – ADG, I – between days 26 and 29, II – between days 29 and 32, III – between days 32 and 35, IV – between days 35 and 38

Fig. 2

Effects of LPS treatments on lymphoid organ indexes of SD rats. A – spleen weight, B – thymus weight, C – the ratio of spleen to body, D – the ratio of thymus to body. The following symbols indicates significant changes in lymphoid organ indexes (P < 0.05): * spleen and thymus differences between LPS and control group on the same days, $ – LPS treatment for day 29 versus LPS treatment for days 32, 35, and 38, # – LPS treatment for day 32 versus LPS treatment for days 35 and 38, % – LPS treatment for day 35 versus LPS treatment for day 38

Fig. 3

Effects of LPS treatments on blood parameters of SD rats. A – white blood cells, B – red blood cells, C – lymphocytes, D – lymphocyte percentage, E – neutrophils, F – neutrophil percentage, G – haemoglobin, H – platelets. * means the same as in Fig. 2