Regulation of Hormone Receptor

Abstract

The regulation of hormone receptors is exerted through genetic and environmental factors. Genetic control of hormone receptors is analyzed by studying changes in their characteristics during the ontogeny, phylogeny, and malignant transformation of cells. The pattern of changes in glucocorticoid receptor contents in cytosol fraction during ontogeny is quite different from tissue to tissue. In the rat's lung tissue, glucocorticoid receptor contents are high during the fetal period and decrease promptly after birth, whereas the contents in the rat's liver are low during the fetal life and start to increase after birth. Glucocorticoid receptors in thymocytes of rats during T-cell differentiation increase transiently, which gives a high sensitivity to steroid treatment in the immature thymocytes. The induction of glucocorticoid receptors in different tissues at different stages of life is strictly controlled by the genetic program. Whether the induction is mediated by humoral factor(s) remains to be clarified. Amounts of glucocorticoid receptors in a particular tissue are subjected to species differences. In a group of steroid-sensitive animals such as the rat, mouse, rabbit and hamster, the amount of glucocorticoid receptors in liver sytosol is rich, whereas it is poor or undetectable in a group of steroid-resistant animals, such as the human, monkey, dog and guinea-pig. Changes in hormone receptors are also observed in malignant tumors. Under certain circumstances, hormone receptors "appear" in malignant tumors originated from organs in which no detectable hormone receptor is observed. These tumors may be called hormone receptor-producing tumors. Environmental factors are also important in regulating hormone receptors. Down regulation of hormone receptors is observed in insulin and glucocorticoids.