Localization of tritiated 1,25-dihydroxy vitamin D3 in fetal rat mandible, kidney, and intestine

In the fetal rat the specific uptake of this hormone appears in the kidney and in the mandible-tooth germ, but not by the intestine. Furthermore, uptake by the two former tissues was greatly influenced by gestational age. Localization in the mandible and tooth germ increased from approximately 50 DPM/mg wet weight of tissue on day seventeen of gestation to over 300 DPM/mg wet weight on the nineteenth day. A similar, but not as dramatic, increase occurred in the kidney. Thus, these data demonstrate: (1) the development of the specific uptake of 1,25-dihydroxy vitamin D3 in the kidney and bone with gestational age, and (2) the absence of specific receptive sites in the fetal intestine.