Compensatory renal growth in the solitary kidneys of Danforth mice with genetic renal agenesis

Purpose: Previously the upper urinary tract anatomy has been characterized in Danforth mice spontaneous murine mutation. This mutation results in unilateral renal agenesis in 30% of the heterozygous offspring. Whether compensatory renal growth occurs in the remaining solitary kidney was assessed. Materials and Methods: Heterozygous pairs of Danforth mice were mated. Of 99 kidneys recovered from adult offspring (8 weeks old) 41 were fixed in Bouin's solution, weighed, sectioned at 8 mu., Stained and prepared for morphometry. An additional 6 kidneys recovered near term (gestational day 18) were processed in the same fashion. The kidneys from the mice without the mutation served as controls. Morphometric analyses were performed using computer software. The size and the distribution of glomeruli were studied. Results: The kidney-to-body weight ratio in the mice with 2 kidneys varied between 1.286 and 2.198 (mean 1.603 +/- 0.33). There were 9 solitary kidneys and their weight x 2/body weight ratio varied between 1.744 and 3.779 (mean 2.9583 +/- 0.724). The differences between these 2 groups were statistically significant (p = 0.003). In addition, the mean cross sectional areas in solitary kidney glomeruli was 13.2% greater than those in bilateral kidneys. Conclusions: Previously described models of compensatory renal growth relied on surgically inducing varying degrees of renal ablation in intact animals: with 2 kidneys, which introduced numerous variables in the study of a complex problem. The results demonstrate that the naturally occurring solitary kidneys of the Danforth mice undergo compensatory renal growth. Furthermore, this growth is initiated early in utero. The lack of anesthetic and surgical manipulation may make this an attractive, reliable and readily available model for the study of compensatory renal, including in utero, growth.