Contribution of Endothelin-1 to Renal Vasoconstriction in Unilateral Ureteral Obstruction: Reversal by Verapamil

Assessment of renal function in mice with unilateral ureteral obstruction using 99mTc-MAG3 dynamic scintigraphy

Background

Renal scintigraphy using ^99mTc-mercaptoacetyltriglycine (^99mTc-MAG3) is widely used for the assessment of renal function in humans. However, the application of this method to animal models of renal disease is currently limited, especially in rodents. Here, we have applied ^99mTc-MAG3 renal scintigraphy to a mouse model of unilateral ureteral obstruction (UUO) and evaluated its utility in studying obstructive renal disease.

Methods

UUO mice were generated by complete ligation of the left ureter. Sham-operated mice were used as a control. Renal function was investigated on days 0, 1, 3, and 6 post-surgery using dynamic planar imaging of ^99mTc-MAG3 activity following retro-orbital injection. Time-activity curves (TACs) were produced for individual kidneys and renal function was assessed by 1) the slope of initial ^99mTc-MAG3 uptake (SIU), which is related to renal perfusion; 2) peak activity; and 3) the time-to-peak (TTP). The parameters of tubular excretion were not evaluated in this study as ^99mTc-MAG3 is not excreted from UUO kidneys.

Results

Compared to sham-operated mice, SIU was remarkably (>60%) reduced in UUO kidneys at day 1 post surgery and the TACs plateaued, indicating that ^99mTc-MAG3 is not excreted in these kidneys. The plateau activity in UUO kidneys was relatively low (~40% of sham kidney’s peak activity) as early as day1 post surgery, demonstrating that uptake of ^99mTc-MAG3 is rapidly reduced in UUO kidneys. The time to plateau in UUO kidneys exceeded 200 sec, suggesting that ^99mTc-MAG3 is slowly up-taken in these kidneys. These changes advanced as the disease progressed. SIU, peak activity and TTPs were minimally changed in contra-lateral kidneys during the study period.

Conclusions

Our data demonstrate that renal uptake of ^99mTc-MAG3 is remarkably and rapidly reduced in UUO kidneys, while the changes are minimal in contra-lateral kidneys. The parametric analysis of TACs suggested that renal perfusion as well as tubular uptake is reduced in UUO kidneys. This imaging technique should allow non-invasive assessments of UUO renal injury and enable a more rapid interrogation of novel therapeutic agents and protocols.

Comparison of the protective effects of papaverine, lidocaine and verapamil on the sperm quality of the testis after induced torsion-detorsion in rats

OBJECTIVE

Spermatic cord torsion is a true urological emergency. Significant subfertility exists in patients following unilateral testicular torsion. Several studies have tested several agents such as vasodilators and antioxidants to inhibit or temper testicular damage.

MATERIAL AND METHODS

Sprague-Dawley rats were divided into five groups; in group 1 (control) no operation or drug injection was done. In groups 2-5 the left testis was subjected to 270 torsions. Two hours after induced torsion, drugs were injected intraperitoneally. Rats in group 2 received no drug, whereas those in groups 3, 4 and 5 were administered a single dose of papaverine (35 mg/kg), lidocaine (4 mg/kg) and verapamil (0.1 mg/kg), respectively. Thirty minutes after drug injection (2.5 h after torsion), testis detorsion was performed in all groups. The drug injections continued for 1 week. After 20 days, bilateral orchiectomy was carried out and semen from both testes was evaluated.

RESULTS

In animals treated with verapamil, left testis sperm count and the percentage of motile sperm were increased significantly in comparison with the sham-operated animals. Sperm morphology in all groups was in the normal range. Mean sperm count and motility in the right testes were not significantly different in different groups.

CONCLUSIONS

Verapamil can induce beneficial effects on semen analysis parameters after testicular torsion in rats.

Verapamil prevents the apoptotic and hemodynamic changes in response to unilateral ureteral obstruction

INTRODUCTION

Obstruction of the urinary tract has marked effects on renal blood flow, glomerular filtration rate (GFR), and tubular function. Moreover, ureteral obstruction results in an injury response that can progress to irreversible renal fibrosis and tubular atrophy by apoptosis.

METHODS

We examined the effect of a calcium channel blocker (verapamil) on renal functions and the abundance of apoptotic (p53, Fas, proliferating cell nuclear antigen [PCNA]) markers 1 week after Unilateral Ureteral Obstruction (UUO).

RESULTS

Immunohistochemistry studies revealed that UUO was markedly associated with up-regulation in the expression of p53 (1550 +/- 82 vs 100 +/- 23%), Fas (657 +/- 48 vs 100 +/- 31%), and proliferating cell nuclear antigen (945 +/- 70 vs 100 +/- 17% of sham levels). Administration of verapamil normalized the up-regulation of apoptotic markers p53 (724 +/- 116 vs 1550 +/- 82%); Fas (162 +/- 38 vs 657 +/- 48%) and PCNA (353 +/- 54 vs 945 +/- 70%). Furthermore, tubular diameter, as an important marker for detecting tubular atrophy was significantly decreased compared to those in UUO rabbits. The percent area of interstitial fibrosis in UUO kidneys was significantly greater than that in Verapamil-treated kidneys. Importantly, Verapamil reduced the development of interstitial fibrosis in UUO rabbits. We measured the GFR and renal blood flow in UUO. Short-term Verapamil challenge partially prevented the decrease in GFR (non-treated UUO: 62 +/- 14; Verapamil + UUO: 119 +/- 7; Sham: 127 +/- 23 microL x min(-1) x kg body wt(-1), P < 0.05) and renal blood flow (non-treated UUO: 1.1 +/- 0.4; Verapamil + UUO: 5.0 +/- 0.2; sham: 6.3 +/- 0.2 mL x min(-1) x kg body wt(-1), P < 0.05).

CONCLUSION

Verapamil significantly prevents impairment in renal function and also prevents the up-regulation of p53, Fas, and PCNA during UUO, demonstrating a marked renoprotective effect of Verapamil treatment in conditions with urinary tract obstruction.

Diagnosis of Ureteropelvic Junction Obstruction in Children: Role of Endothelin-1 in Voided Urine

OBJECTIVES

To examine the role of voided urine endothelin-1 (ET-1) in the diagnosis and follow-up of children with ureteropelvic junction obstruction.

METHODS

The study included 35 children with unilateral ureteropelvic junction obstruction who underwent pyeloplasty and 30 control children, including 10 healthy children, 10 with vesicoureteral reflux, and 10 with renal stones. Voided urine samples were obtained from the children in the study group before surgery and from the renal pelvis by needle aspiration during pyeloplasty. Bladder urine samples were also collected from the study group 1, 2, 3, 6, 9, and 12 months postoperatively. Bladder urine samples were also collected from all 30 control children. ET-1 was measured in the urine samples collected from the study and control groups.

RESULTS

The preoperative ET-1 level in the voided urine of the study group was significantly greater than its level in each of the three control groups. For the whole study group, a cutoff value of 3 fmol/mg creatinine gave a sensitivity of 74.3%, a specificity of 90%, and an overall accuracy of 81.5%. In 8 children (1 year old or younger), a cutoff value of 4 fmol/mg creatinine gave a sensitivity and specificity of 100%. Compared with the preoperative value, ET-1 had decreased significantly at 12 months after pyeloplasty.

CONCLUSIONS

The ET-1 level in voided urine is a useful marker that could be used as a noninvasive tool for the diagnosis and long-term follow-up of children with ureteropelvic junction obstruction.

Evaluation of intrarenal blood flow by Doppler ultrasonography immediately after extracorporeal shock wave lithotripsy on hydronephrotic kidney

Extracorporeal shock wave lithotripsy (ESWL) is an effective and relatively noninvasive mode of treatment for urinary calculi. The aim of this study was to test whether therapeutic ESWL induces changes in renal parenchymatous blood flow and to evaluate shock wave side effects on the renal parenchyma. A total of 45 patients who underwent ESWL for ureteropelvic stone between January 2002 and July 2003 were included in this prospective study. Color Doppler sonography before and 30 minutes after ESWL showed no significant morphologic change. Resistive index (RI) was used to estimate renovascular resistance. The RI significantly increased in obstructed hydronephrotic kidneys. However, no significant change was observed in both treated and untreated kidneys before and after treatment. Hydronephrotic kidneys do not have a higher risk of post-ESWL renovascular resistance interference. The measurement of changes in RI with Doppler ultrasonography may provide useful information for clinical diagnosis of renal tubulointerstitial and vascular damage.

Alterations of Renal Hemodynamics in Unilateral Ureteral Obstruction Mediated by Activation of Endothelin Receptor Subtypes

PURPOSE

Unilateral ureteral obstruction (UUO) for 21 hours causes severe renal vasoconstriction. We examined the role of endothelin (ET)-A receptor in renal hemodynamic alterations induced by UUO.

MATERIALS AND METHODS

Hemodynamic and clearance experiments were performed in 3 groups of anesthetized dogs. In group 1, 6 sham operated dogs received intrarenal infusion of the specific ET-A receptor antagonist BQ-610 (Peninsula Laboratories, Inc., Belmont, California), followed by infusion of the nitric oxide synthase substrate L-arginine. In the 7 group 2 dogs release of 21-hour UUO was followed by intrarenal infusion of BQ-610 and L-arginine. In the 5 group 3 dogs release of 21-hour UUO was followed by L-arginine infusion.

RESULTS

UUO caused marked decreases in renal blood flow (RBF) and glomerular filtration rate (GFR) in groups 2 and 3 compared with group 1. In group 1 BQ-610 and L-arginine infusion did not alter RBF or GFR. In contrast, BQ-610 infusion in group 2 after UUO release led to a significant increase in RBF and GFR as well as additional increases after L-arginine infusion. After UUO release in group 3 L-arginine infusion alone did not change RBF or GFR.

CONCLUSIONS

After UUO release blockade of the ET-A receptor ameliorates renal vasoconstriction. The addition of L-arginine, which is a substrate for nitric oxide synthase, superimposed on ET-A receptor blockade confers a further decrease in renal vascular resistance, suggesting that the ET and L-arginine-nitric oxide systems are involved in renal hemodynamic alterations caused by UUO.

Predictive value of renal histological changes for postoperative renal function improvement in children with congenital ureteropelvic junction stenosis

BACKGROUND

The aim of this study was to evaluate the relationship between renal function, as measured by diuretic radionuclide renography, and the outcome of pyeloplasty. A study was designed to evaluate renal parenchymal biopsy specimens derived from children undergoing corrective surgery for ureteropelvic junction (UPJ) stenosis, and compare these to preoperative and postoperative renal function status.

METHODS

Thirty-five children with congenital unilateral UPJ stenosis were evaluated. In addition to all conventional diagnostic procedures for UPJ stenosis, differential renal functional (DRF) activity was assessed in each of these children by obtaining 99mTc diethylenetriaminepentaacetic acid renogram curves. All children underwent dismembered pyeloplasty, and follow-up renogram evaluation was conducted 6 and 12 months after surgical repair. Biopsy specimens from renal cortical regions obtained during the surgical correction of UPJ stenosis were evaluated, and changes in renal histology were graded from I to V according to their severity. Spearman's correlation test was used to compare the histological evaluation results and the basal, 6- and 12-month follow-up DRF findings. A Wilcoxon paired test was used to evaluate statistical differences between values.

RESULTS

The findings showed a positive correlation between the severity of histological changes and DRF activity. All kidneys (22) with a DRF activity value of < 40% preoperatively demonstrated at least grade III changes when biopsy specimens were examined. Of children with a DRF activity value > 40% (13), only three showed severe histological changes. Histological grades were correlated between basal (r = -0.4; P = 0.019), 6-month (r = 0.54; P = 0.002) and 12-month (r = 0.54; P = 0.02) findings. In the Wilcoxon paired test, there was a statistically significant difference between basal and 6-month values (P < 0.05), and also between basal and 12-month values (P < 0.01). There was no statistically significant difference between 6- and 12-month values (P > 0.20).

CONCLUSION

Comparative evaluation of postoperative renal function with DRF activity and renal parenchymal histological alterations revealed a close correlation in terms of renal function improvement potential following reconstructive surgery in children with UPJ stenosis.

Obstructive uropathy

Recent study has increased the understanding of the physiological processes occurring in obstructive uropathy, in particular the role played by vasoactive mediators and cellular mechanisms. There is an emphasis on developing effective and less invasive means of detection and treatment of ureteric obstruction, although it remains to be determined how the techniques currently being assessed will impact on clinical practice.