Enhancing effect on N-nitrosodimethylamine-induced tumorigenesis by unilateral hydronephrosis.

The effect of unilateral hydronephrosis (U-HN) on chemical tumorigenesis by two im injections of N-nitrosodimethylamine (DMN; CAS: 62-75-9) with the use of inbred female W rats was studied. Of the rats in the U-HN group, 70.0% developed kidney tumors, 25.0% developed mammary tumors, 20.0% developed hepatomas, and 20.0% developed other tumors. Almost all kidney tumors in the U-HN group (96.0%) were induced in the compensatory (contralateral) kidney. In contrast, of the rats in the unilateral nephrectomy (U-NR) group, 29.4% developed kidney tumors, 11.8% developed mammary tumors, 23.5% developed hepatomas, and 11.8% developed other tumors. Rats in the sham-operated group developed 1 small kidney tumor (7.7% of the rats) but no tumors in other organs. Thus, under these conditions, U-NR and especially U-HN strongly increased tumor induction in DMN tumorigenesis not only in the compensatory kidney but also in extrarenal organs.