Scanning electron microscopy (SEM) observations of urinary cytology from rats fed N [4 (5 nitro 2 furyl) 2 thiazolyl] formamide (FANFT)

Rats fed FANFT undergo progressive changes of the urinary bladder mucosa from mild hyperplasia to invasive carcinomas. These changes when followed by SEM range from elevation of luminal cell surfaces and variation in cell size to the appearance of increasing proportions of microvilli. Urine cytology was examined after 4, 10, 14 and 20 wk of FANFT feeding to male weanling Fischer rats at a dose of 0.2%. Urine was collected on ice in flasks containing 2% glutaraldehyde from rats housed in metal urine collection cages with water and food available ad libitum. Urine was processed through sintered silver filters of several pore sizes and processed for SEM. Normal epithelial cells in the urine were characterized by SEM as having a surface composed of well developed microridges, being relatively uniform in size, and occurring singly. Tumor cells were present singly or in clumps with marked variation in cell size and shape and with cell surfaces predominantly covered with microvilli. With more advanced lesions seen in rats fed control diet for 23 wk after 20 wk of FANFT, numerous red and white blood cells and bacteria were in the urine. The cytology observed by SEM at different time intervals correlated with the changes seen in bladders examined at the same times by SEM.