Influence of chronic oestrogen treatment on severity of hydronephrosis in inbred DDD mice

It has been reported that mice treated chronically with oestrogen (oestradiol propionate) increase their bladder urine volume. Since inbred DDD mice, particularly male DDD mice, lack a protective mechanism against vesicoureteral reflux (VUR), chronic oestrogen treatment may increase the pressure in the renal pelvis and lead to severe hydronephrosis. The present studies were carried out to confirm this hypothesis. Results of a least-squares analysis of variance showed that the severity of hydronephrosis was more severe after treatment with high doses of oestrogen (1.0 and 5.0 mg/kg/week) in entire and castrated male DDD mice. Hydroureter was also observed in the same groups. Intra-vesicular pressure was 7 to 12 cmH2O higher in mice of these groups than in control DDD mice. High doses of oestrogen had no effect on the kidneys of C57BL/6 mice which showed normal protection against VUR, though it increased bladder urine volume. These findings support the hypothesis that hydronephrosis in DDD mice is caused by an incomplete protective mechanism against VUR.