[Karyometry of BBN-induced precancerosis of the urothelium : An experimental analysis].

The morphology of experimental precancerous lesions of the urinary bladder has been interpreted quite differently by various authors.The aim of this investigation was to quantify these lesions by karyometry and, thus, to gain a more reliable understanding of the process.A total of 60 Wistar rats were fed with N‑butyl-N-(4-hydroxybutyl)nitrosamine (BBN) at a concentration of 0.05 % in their drinking water to induce preneoplastic changes of the urothelium. After the second week of BBN exposition, 6 animals were killed every 2 weeks up to week 20. Smears of the scraped off urothelium of 3 urinary bladders of each group were analyzed cytologically and karyometrically.BBN exposition led to statistically significant changes of the karyometric values using the χ2 test to differentiate the control animals from the ones that had ingested BBN and the 2‑week groups from each other. These changes consisted mainly in significant deviations of the size of the nuclear area within the different groups.Morphological and karyometrical analysis showed that biologically relevant stages in the development of chemically induced urothelial precancerous lesions could be realized much earlier than had been assumed in recent publications. Karyometric analysis offered a valid basis to describe the early morphologic alterations of carcinogenesis.