Answer
The number of hormone receptors on a target cell may very widely -- 2,000-100,00. Down-regulation takes place when there is an excess of hormone. In such a case, the number of receptors on the target cells decreases. For example , if there is a great amount of luteinizing hormones in testicular blood the number of receptors per target cell may decrease to make the target cells less sensitive to the hormone.
Work Step by Step
The process of up-regulation produces opposite effects to those produced by down-regulation.. If there is an insufficient amount of a hormone in an area, the number of receptors per target cell will increase to make the cells mores sensitive. An example is the increase of oxytocin receptors on uterine myometrial cells during the third semester of pregnancy. Also, when one exercises, the number of insulin receptors on certain target cells are upregulated.
