Glucocorticoid receptors in isolated intestinal epithelial cells in rats.

Abstract

There is evidence that glucocorticoid hormones influence a variety of epithelial cell functions in the small intestine. To exert their effect, glucocorticoids bind to cytoplasmic glucocorticoid receptors (GR), which, following translocation to the nucleus, stimulate mRNA transcription and then protein synthesis and ultimately trigger hormonal actions. To determine the distribution of GR in small intestinal villus and crypt cells, we measured GR activity in enriched villus and crypt cell fractions by use of [3H]dexamethasone. In normal rats GR activity was present in all cell fractions but was lowest in fully mature villus cells of the upper villus and greatest in immature crypt cells. In contrast, 1 wk after adrenalectomy and ovariectomy or sham operation, both of which reduced plasma corticosterone levels, GR activities were comparable in enriched villus cell and enriched crypt cell fractions. Kinetic studies indicated a single class of binding sites with comparable Kd values in villus and crypt cells of normal and steroid-depleted animals, suggesting that there are more glucocorticoid-binding sites in crypt than in villus cells of normal animals. Immature crypt cells may be more susceptible to glucocorticoid modulation than fully mature villus cells in normal rats in view of their higher GR activity.