The significance of the dilated renal pelvis in the nitrofen-exposed rat fetus: effects on morphology and function.

Previously (R. J. Kavlock, B. F. Rehnberg, and E. H. Rogers, 1987, Teratology 36, 51-58) we reported that gestational exposure of rats to adriamycin induced alterations in development of the fetal renal papilla that persisted postnatally. The morphological effect was associated with functional deficits in neonatal animals as seen by their performance during a test of renal concentrating ability in the second postnatal week. In the present study, we utilized an experimental approach similar to that in the adriamycin study to evaluate the fate of the dilated renal pelvis that is induced in fetal rats following prenatal exposure to nitrofen. Groups of Long-Evans rats were exposed to 0, 6.25, 12.5, or 25 mg/kg of nitrofen on gestation Days 7-16. Renal morphology of the offspring were determined on gestation Day 21 and postnatal Week 5. The postnatal cohort was tested in the second postnatal week for their ability to excrete an osmotically concentrated urine. As was the case with adriamycin, the renal concentrating ability in the neonate was reduced and poor performance in the function test was associated with permanence of the morphological effect. By utilizing a standardized semiquantitative procedure to describe the status of the kidneys and ureters during development in combination with physiological assessment of organ performance, we were able to assess the morphological and functional development of the kidney. In the absence of other anomalies we suggest that offspring be monitored during postnatal development when alterations of the fetal renal papilla are observed in standard teratology bioassays in order to determine whether the effect is transient or permanent.