Postnatal evaluation of morphological and functional effects of prenatal exposure to nitrofen in the Long-Evans rat.

The herbicide Nitrofen was administered to Long-Evans rats on d 11 of gestation (75 mg/kg, po) in an effort to further evaluate its reported ability to induce hydronephrosis and to affect Harderian-gland development. This regimen did not affect the litter size at birth or postnatal growth and viability. Eye opening, recorded on postnatal d 16 (PD 16), figure-eight maze activity (PD 24), and vaginal opening (PD 31) were unaffected by treatment. Lung weights were lower on PD 7 and 35 but not at PD 210. Harderian-gland weights were lower at PD 35 and 210, and 12% of the Nitrofen-treated offspring had missing glands, versus 0% of controls. Hydronephrosis was detected in 23% of the necropsied offspring and was represented in every treated litter. Only one control pup (1.5%) was hydronephrotic at necropsy. Treated pups, regardless of the presence or absence of hydronephrosis, had a diminished ability to concentrate urine in fluid deprivation tests applied on PD 3 and 6. By PD 50, however, treated offspring were not deficient in a similar test unless hydronephrosis was present. Microscopic examination on PD 7 of morphologically normal kidneys showed no treatment-related delay in nephrogenesis. Serum chemistry values evaluated at PD 210 showed no overall treatment effect, but animals with hydronephrosis had elevated phosphorus, urea nitrogen, creatinine, and potassium levels. This study has demonstrated that a single prenatal exposure to Nitrofen alters Harderian-gland development, lung growth, and renal development and function. Hydropenia tests applied to neonates detected renal dysfunction and were predictive of hydronephrosis, while a similar test in young adults did not detect dysfunction in morphologically normal animals. The neonatal hydropenia test appears to be an extremely useful tool in evaluating perinatally induced renal dysfunction.