Abstract: Objective To investigate the effect of losartan,an angiotensin II type-1 receptor(AT1R)antagonist,on the levels of angiotensinⅡ(AngⅡ)and AT1R in diabetic rat kidney.Methods Male Wistar rats were divided into 3 groups,group A(n=11)served as the control group,group B(n=11)included the diabetic rats(induced by intraperitoneal injection of streptozotocin)without any therapy,and group C(n=9)diabetic rats treated with losartan.After 18 weeks of treatment,the kidneys were taken from all the rats to measure the expression of AT1R mRNA by RT-PCR and detect the AngⅡ level.Blood was also drawn from the heart to measure AngⅡ level,and 24-hour urine was collected to measure albumin level(urine albumin excretion,UAE)with rat albumin enzyme immunoassay kit.Results The blood and renal AngⅡ levels showed no significant difference between the 3 groups.The expression of renal AT1R mRNA in group B(0.62±0.17)was significantly lower than that in group A(1.13±0.82,P<0.01)and group C(1.13±0.62,P<0.01).UAE in group B(2.18±1.98 mg)was significantly higher than that in group A(0.41±0.47 mg/d,P<0.01)and C(0.65 ±0.89 mg/d,P<0.01).Conclusion Losartan can increase the expression of AT1R mRNA in diabetic rat kidneys without altering the blood and renal AngⅡ levels.