Increased intestinal chromatin template activity. Influence of 1alpha,25-dihydroxyvitamin D3 and hormone-receptor complexes.

Abstract

la,25-Dihydroxyvitamin D, administration to rachitic chicks results in an increase in the chromatin template activity of intestinal target tissue assayed in uitro using Escherichia coli RNA polymerase. The maximum stimulation of template capacity was 12 to 20% over control values and occurred 2 hours after administration of the sterol. This rapid effect preceded the biologic response to la,25-dihydroxyvitamin D, in the intestine and was not observed in other tissues such as liver or kidney. The in uiuo enhancement of intestinal chromatin template activity was specific for the la,25-dihydroxyvitamin D, hormone in that equivalent doses of 25-hydroxyvitamin D, or vitamin D, did not elicit a response in 2 to 3 hours. Only lot-hydroxyvitamin D,, a synthetic sterol which is very rapidly metabolized to the lcu,25-dihydroxyvitamin D, form, was able to mimic the natural hormone in uiuo.