OBJECTIVE:To study the effects of rhei radix and astragali radix on renal protection and intestinal barrier function in rats with chronic renal failure(CRF),and analyze its pharmacological mechanism from the theory of"gut-renal axis"in TCM. METHODS:Rat models of CRF were established by 5/6 nephrectomy. Rats were randomly divided into sham operations group (group J,n=6),model group(group M,n=8),and administration groups(n=9),which included benazepril group(group Y, positive control,2 mg/kg),rhei radix high-dose,medium-dose,low-dose groups(group DH,DM,DL,calculated by crude drug as 3,1.5,0.75 g/kg),and astragali radix high-dose,medium-dose,low-dose groups (group HH,HM,HL,calculated by crude drug as 6,3,1.5 g/kg). After 1 week of modeling,rats in each administration group were intragastrically administrated,once a day,for 5 weeks. Rats in group J,M were intragastrically administrated equal volume distilled water. After 12 h of administration, the 24 h urine protein(Upr),serum levels of creatinine(SCr),urea nitrogen(BUN),uric acid(UA)and plasma endotoxin level were detected,and kidney index was calculated. Changes in renal tissue,villi of small intestinal mucosal tissue and crypt depth were observed by microscope. RESULTS:Compared with group J,24 h urine volume and 24 h water drinking volume of rats in group M were increased,24 h Upr,serum levels of SCr,BUN,UA,plasma endotoxin level,and kidney index were increased, with statistical significances(P<0.05 or P<0.01). Most glomerular volume were increased and rigid in group M,showing intersti-tial infiltration in large number of inflammatory cells;villus length,villus width,mucosal thickness and villus length/crypt depth ra-tio of intestinal mucosa were decreased (P<0.05 or P<0.01),and crypt depth was increased (P<0.01). Compared with group M,24 h urine volume in group DM,DL,HM,HL was decreased;24 h water drinking volume in group HM was decreased;24 h Upr,serum levels of SCr,BUN levels,and kidney index of rats in each administration group were decreased. Except for group HH,serum UA levels in other administration groups was decreased;and except for group HH,HM,HL,plasma endotoxin level in other administration groups was decreased,with statistical significances(P<0.05 or P<0.01). The pathological morphologies of renal tissue,intestinal mucosal tissue and intestinal villi in each administration group were improved to varying degrees. CONCLU-SIONS:Both rhei radix and astragali radix can effectively reduce the metabolic toxin levels of rats,improve filtration function of glomerular and enhance the exclusion of metabolic trash,which may be restoring the intestinal function to achieve the goal of treat-ing CRF. And both show optimal effect in medium dose.