Paracrine signalling
From Free net encyclopedia
Paracrine signalling is a form of cell signalling in which the target cell is close to the signal releasing cell, and the signal chemical is broken down too quickly to be carried to other parts of the body. The signal chemical is called the paracrine agent. Examples of paracrine signalling agents include growth factor and clotting factors. Growth factor signalling plays an important role in many aspects of development. In mature organisms paracrine signalling functions include responses to allergens, repairs to damaged tissue, formation of scar tissue, and clotting. Overproduction of some paracrine growth factors has been linked to the development of cancer. Other examples of paracrine agents are somatostatin and histamine.
Some paracrine agents also have autocrine or endocrine actions as well. For example, testosterone secreted from the testes acts in an endocrine manner to stimulate peripheral events (e.g. muscle growth), and in a paracrine manner to stimulate spermatogenesis in the adjacent seminiferous tubules.