- Paracrine signalling
Paracrine signaling is a form of
cell signaling in which the target cell is near ("para " = near) the signal-releasing cell.A distinction is sometimes made between paracrine and
autocrine signaling . Both affect neighboring cells, but whereas autocrine signaling occurs among similar cells, paracrine signaling affects other kinds of cells.Local action
Some signaling molecules degrade very quickly, limiting the scope of their effectiveness to the immediate surroundings. Others affect only nearby cells because they are taken up quickly, leaving few to travel further, or because their movement is hindered by the
extracellular-matrix .Examples
Growth factor andclotting factor s are paracrine signaling agents. The local action of growth factor signaling plays an especially important role in the development of tissues. In insects,Allatostatin controls growth though paracrine action on the corpora allata.In mature organisms, paracrine signaling is involved in responses to
allergen s, tissue repair, the formation ofscar tissue , and bloodclotting .The overproduction of certain paracrine growth factors has been implicated in the pathology of
cancer .Somatostatin andhistamine are paracrine agents.Autocrine and endocrine actions
Some paracrine agents also have autocrine,
intracrine orendocrine actions.For example,
testosterone secreted from thetestes acts as an endocrine agent to stimulate peripheral events, such as muscle growth, and as a paracrine agent to stimulatespermatogenesis in the adjacentseminiferous tubules .ee also
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Endocrine system External links
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* DorlandsDict|six/000078100|paracrine
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