Abstract: Objective To investigate the growth pattern of ureteric bud (UB) and nephron number induced by UB in developing mouse kidney. Methods Immunohistochemical technology and stereological method were used to observe and measure UB and nephron at different developmental stages of embryonic and postnatal mice. Results Immunohistochemical examination showed that ureteric buds surrounded by metanephrogenic tissue were observed in embryonic day 12, and each UB tip branched dichotomisously. In embryonic day 14, nephrons induced by UB emerged. From embryonic day 16 to postnatal day 5, the number of UB tip and nephrons were increased. In postnatal 7, UB disappeared and nephron number was not changed. Stereological examination showed that from embryonic day 14 to 18, each UB tip induced one nephron . From postnatal day 1 to 5, each UB tip induced four nephrons. Those data indicated that a total of 10-11 UB branching events occurred during mouse kidney morphogenesis.Conclusion It is well established that nephron number is proportional to the extent of UB branching that occurs during developing kidney, but it is not constant.

Key words: Ureteric bud, Nephron, Development, Immunohistochemistry, Mouse