Immunohistochemical localization of calbindin‐D28k during the development of the rabbit nephron

Specific antibodies raised against a 28‐kilodalton chick intestinal calcium‐binding protein (calbindin‐D28k) were used to localize the protein immuno‐cytochemically in the developing rabbit kidney. Kidneys taken from rabbits between the 13th embryonic and 17th postnatal day were examined. Calbindin‐D28k was observed in the mesonephric duct and the ureteral bud on the 13th embryonic day. During subsequent involution of the mesonephros, the ampullae of the metanephric ureteral buds contained calbindin‐D28k. The protein was gradually lost from the ureters and the deep interstitial collecting ducts. Calbindin‐D28k was never present in the renal vesicles derived from the nephrogenic blastema, but it was present in the connecting tubule segments during formation of the arcades. The last finding supports the belief that the connecting tubule is derived from the ureteral bud.