Vitamin D-dependent calcium binding protein in the chick brain

A radioimmunoassay for chick CaBP has been used to measure the distribution of the protein in the chick central nervous system. The cerebellum contained 7.4 μg/mg protein, six times more than the medulla, and eleven times more than the cerebral cortex. Most of the CaBP was found in the supernate, after ultracentrifugation, with only trace amounts in the secretosome, microsome and other fractions. Slices of cerebellum from 19 and 21 days $\text{in}$$\text{ovo}$ chicks were maintained in organ culture. Treatment with kainic acid resulted in a loss of CaBP from the slices while metabolites of vitamin D were without effect.