Abstract: Objective To observe the effect of chronic salt loading on the remodeling of thoracic aorta in spontaneously hypertensive rats and to investigate possible mechanism.Methods Spontaneouly hyperten sive rats(SHR)(n=80,male,4-5 weeks old)were assigned randomly to receive 4% high salt(HS group,n=45)and 0.4% low salt(LS group,n= 35)for 16 weeks.Blood pressure,urine volume,and urinary sodium excretion were measured every four weeks.The rats were sacr ificed randomly at the start,the 4 th,8th,12th,16th week of the study.The aorta samples were collected and dyed with haema to xylineosin(HE)to observe the change of aorta with micro scope.The microholog raphy system was used to mea sure the wall thickness(WT)and luminal diameter(LD)and to calculate the ratio of wall th ickness to luminal diameter (WT/LD).Expression of transforming growth factor-beta 1(TGF-β1)and endothelialnitric oxide synthase(eNOS)in the aorta were measured with immunohistochem istry method.Results The wall thickness(WT)in HS group were increased compared with that of LS group with significant differences between the two groups at 8th,12th,and 16th week(117.0±8.8 vs 100.5±9.1,124.7±8.8 vs 111.7±13.0,168.1±32.7 vs 132.5±32.6 m;P<0.05 for all)Compared with LS group,the TGF-β1 average light densities was increa sed at 4th,8th,12th,and 16th week(11795.8±1079.4 vs 9240.7±930.7,17773.8±928.3 vs 16608.5±620.2,6019.4±433.4 vs 5052.9±865.7,and 5455.6±380.2 vs 4372.8±579.1; P<0.05 for all).The eNOS averag elight densities were increased(14970.1±1249.2 vs 12638.1±1201.2,18236.6±2723.9 vs 14487.1±240.7,7201.9±1006.5 vs 5352.5±1251.5,and 8068.2±1418.2 vs 5213.1±2224.9;P<0.05 for all).Conclusion Chronic salt loading could agg ravate the vascular remodeling in SHR.Local TGF-β1 induced by salt loading in SHR is probably involved in the development of the vascular remodeling.