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[Effects and mechanisms of 6-week intensive training on renal function in rats].

OBJECTIVE
To study the effect of 6-week intensive training on renal function in rats and the mechanism of exercise-induced proteinuria.


METHODS
Thirty-six male SD rats, aged 6 weeks, were divided into two groups, including a control group(C,n=12)and an overtraining group(M,n=24). After the rats adapted to feeding for 4 d, group C did not carry out any exercise, and the M group did 6-week of increasing load swimming, 6 days a week, once a day. Started with the load of 1%weight at the beginning of the 4th week,and gradually increased (to 6% weight). Took a single urine from both groups 30 min after the end of the training. Blood was taken from the main ventral vein, and the bilateral kidneys were to be tested. The levels of tested urine protein, microalbumin and neutrophil gelatinase associated lipocalin(NGAL) was determined by using enzyme linked immunosorbent assaytest. The content of urine creatinine was tested with alkaline picric acid method,. The serum levels of colorimetric method to determine serum creatinine and urea nitrogen were determined by colorimetric method. The expression of Nephrin in renal tissue was detected by Western blot and the radioimmunoassay was used to test serum testosterone, corticosterone and renin-angiotensin system related index.


RESULTS
Compared with group C, the serum testosterone/cortisone(T/C) of group M was decreased significantly (P<0.01). The urine total protein(TP), microalbumin (mAlb), microalbumin/creatinine (mAlb/CRE), NGAL, blood urea nitrogen (BUN) and serum creatinine(SCr) were increased significantly (P<0.01). The abnormality of glomerular structure was obvious, and the paller scores were higher. The protein expression of Nephrin was obviously down decreased (P<0.01). The renin activity (Ra) and angiotension Ⅱ (Ang Ⅱ) in renal and circulating blood were decreased significantly (P<0.01).


CONCLUSIONS
The effects of 6-week intensive training on renal function in rats and the mechanism of exercise-induced proteinuria may be that overtraining can induce the continuous excitation of Reninrenin activity in renal and circulating blood, down-regulated the expression of Nephrin, lead to abnormality of renal structure and function, and proteinuria.