Effect of glucocorticoid administration on intestinal, renal, and cerebellar calbindin-D28K in chicks

A radioimmunoassay for chick intestinal calcium-binding protein (calbindin-D28K, CaBP-28K) has been developed in our laboratory with a detection limit of 0.3 ng/ml. The values for CaBP-28K in vitamin D-deficient (-D) chicks ranged from a high value for the cerebellum (21,400 +/- 580 ng/mg protein) to a scarcely detectable level in the liver (19.6 +/- 2.2 ng/mg protein). After administration of vitamin D (vitamin D3 500 IU p.o. for 7 days) (+D), the levels of CaBP-28K increased in the duodenum (52,300 +/- 5,100 ng/mg protein), ileum (45,200 +/- 740 ng/mg protein), cerebellum (22,000 +/- 470 ng/mg protein), colon (15,200 +/- 330 ng/mg protein), and kidney (13,460 +/- 540 ng/mg protein). However, the increment in the level of CaBP-28K in each tissue after vitamin D administration was different; levels of CaBP-28K in the duodenum, ileum, and colon increased dramatically more than 200 times after vitamin D administration, whereas that in the kidney showed only a 2.5-fold increase and was unaltered in the cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)