The Effect Of Different AUR Duration On The Function And Structure Of Bladder In Rats

ObjectiveTo investigate the influence of acute urinary retention(AUR) duration on the function and structure of the bladder in rats;To investigate the effect of different AUR duration on the recovery of the function and structure of the bladder after AUR.Materials and MethodsPart One:AUR was induced in Sprague-Dawley rats by an infusion of saline(twice the threshold volume).According to the duration time,40 SD rats were divided into 5 groups:AUR1 hour(h) group(n=8),AUR2h group(n=8),AUR4h group(n=8),AUR8h group(n=8)) and the control group(n=8).Then to test the bladder function through urodynamics and muscle strip study;To check out the changes in structure of the bladder by hematoxylin-eosin(HE) staining and transmission electron microscopy;To detect the apoptosis rates and apoptosis-related factors of the bladder via TUNEL staining,Westen-blot and RT-PCR in different groups.Part Two:72 SD rats were divided into 3 groups:AUR1h group(n=24),AUR4h group(n=24) and the control group(n=24).At the 3 day,1 week,3 week after AUR,to test the bladder function through urodynamics and muscle strip study;To check out the changes in structure of the bladder by HE,Masson staining and transmission electron microscopy. ResultsPart One:Compared with the control,the maximum detrusor pressure of the bladder in groups with 2h,4h,8hAUR were significantly lower(P＜0.01).In the groups with 2h,4h,8hAUR,the maximal rate of tension generation induced by higher frequency electrical-field stimulation(EFS),higher concentration potassium chloride and carbachol were both significantly lower than those of the control(P＜0.05).The longer the AUR duration was,the lower the maximal rate of tension generation was.With the increase of AUR duration,the inflamation of the bladder tissue was more serious; At the same time,with the increase of AUR duration,the injury of ultrastructure,such as mitochondria was more obvious.Furthermore,with the increase of AUR duration, apoptosis rates keep going up.Pro-apoptotic bax and caspase-3 were up-regulated with the AUR maintaining,while bcl-2 was down-regulated.Part Two:At 3d,1w,3w after AUR,weights of bladder in AUR 4h group were significantly higher than those in AUR 4h group(P＜0.01).The bladder capacity,bladder compliance and the detrusor contractility were almost recovered within 3 weeks in the group with 1h AUR,but they had no improvement in group with 4h AUR.Compared with the control,the maximal rate of tension generation of muscle strip had no obvious changes in group with 1h AUR;While it was significantly lower in group with 4h AUR and didn't get recovery within 3 weeks.Three days after AUR,inflammation of bladder in group with 4h AUR is more serious than that of the group with 1h AUR. Three weeks after AUR,the hyperplasia of fibrous tissue in the group with 4h AUR was more obvious than that in group with 1h AUR.Conclusions1.Different AUR duration time results in different function and structure injury in rat bladder.With the increase of the AUR duration,the inflammation and the injury of ultrastructures are more serious;The number of apoptotic cells and pro-apoptotic factors are going up,while anti-apoptotic factors are going down.All of those could lead a more serious injury in bladder function and structure.2.Different AUR duration time also has different effects on the recovery of the bladder function and structure.Longer AUR duration time can result in more serious injury of bladder structure and more obvious hyperplasia of fibrous tissues,which make it is more difficult to restore the function of bladder after AUR.