How many times can a hormone or growth factor activate its receptor?

Question

Can anyone point me in the direction of some online literature that explains or helps me understand how man times hormones/growth factors can attach to their respective receptors. I know understand the half and active lives of hormones/peptides, but I was curious if after activating its receptor, whether the hormone/growth factors are rendered inactive or if they can continue activation.

Answer 1

This is not a simple question. Some hormones, once they activate the receptor are endocytosed with the receptor into the cell. Therefore, these hormones can only activate the receptor one time.

Other hormones activate receptors inside the cells (e.g. steroid hormones) and again, may stay attached to the receptor as it translocates to the nucleus to activate gene expression.

Lastly, still others may activate a surface receptor and then dissociate from the receptor, making them available to activate the receptor again.

Hope this was helpful. If you go to Pubmed (enter "entrez pubmed" in your search engine), they have access to many online medical texts on cell biology. You can search these books for their chapters and info. on hormones, receptors, etc.

Best wishes.

Answer 2

This is a tough one !! There are many factors that are involved...you may need to narrow your focus..

Ligand-gated channels, G proteins and cAMP are all involved which activate or inactivate the K-Na pump which affects a whole bunch of things. Then you have the whole agonist/antagonist part.

All I can say is that "receptor-mediated responses to drugs and hormonal agonists often desensitize with time". Katzung pg. 23