Gender-dependent disease severity in autosomal polycystic kidney disease of rats.

The impact of gender on the course of chronic renal failure in polycystic kidney disease (PKD) has been under discussion for years. Recently an animal model of autosomal dominant PKD in the rat became available allowing this topic to be studied. The aim of this study was to evaluate disease severity according to gender, and the occurrence of anticipation and/or genetic imprinting. Male and female affected PKD rats were crossed with respective Wistar-Ottawa-Karlsburg (WOK) rats. From this P generation 26 affected F1 hybrids were obtained, which were then backcrossed with WOK rats, resulting in 275 backcrosses (BC generation). In BC rats the affected males had a significantly higher kidney weight, worse histology and poorer renal function than the females. In the male, but not the female rats of the BC generation, transmission from an affected F1 mother resulted in significantly higher kidney weight, worse histology and poorer renal function than when the gene was inherited through an affected father. Since at the same time body and kidney weight were higher in the respective unaffected males, the previous effect in the affected rats might be due to a growth factor transferred by the mother's milk. The sex of the P generation had no such impact on these parameters. Thus our data provide no evidence for disease anticipation and genetic imprinting (in the classical sense) in the PKD rats, and the assumption of a gender-dependent disease expressivity is favored.