Intestinal response to 1α,25,dihydroxycholecalciferol II. A timed study of the intracellular localization of calcium binding protein

Abstract

1. 1. The cell of origin for calcium binding protein was determined by enzyme immunohistochemistry after treatment of rachitic chicks with 1α,25-dihydroxycholecalciferol. 2. 2. Goblet cells did not contain calcium binding protein at any time after treatment. 3. 3. Calcium binding protein appeared first in nuclei and cytoplasm of intestinal absorptive cells at the villus base between 6 and 8 h after treatment. By 18 h, calcium binding protein was found in cells throughout the villus. 4. 4. Pulse labeling of cells with [ 3H]thymidin indicated that the progression of calcium binding protein appearance from villus base to tip was much faster than the cell migration rate. 5. 5. We conclude that both young cells at the base of the villus and more mature cellsat the villus tip are capable of calcium binding protein synthesis, but the young cells respond much faster. 6. 6. After the initial synthetic phase, the apparent relative intracellular concentration of calcium binding protei in a given cell decreases with time, which suggests that calcium binding protein is secreted, degraded by the absorptive cell, or is reoriented in the cell so that the intracellular concentration appears lower.