Paracrine signalling
Encyclopedia
Paracrine signalling is a form of cell signalling
in which the target cell is near ("para" = near) the signal-releasing cell.
and clotting factors are paracrine signalling agents. The local action of growth factor signalling plays an especially important role in the development of tissues. Also, retinoic acid
, the active form of vitamin A
, functions in a paracrine fashion to regulate gene expression during embryonic development in higher animals. In insects, Allatostatin
controls growth though paracrine action on the corpora allata.
In mature organisms, paracrine signalling is involved in responses to allergen
s, tissue repair, the formation of scar tissue
, and blood clotting.
secreted from the testes acts as an endocrine agent to stimulate peripheral events, such as muscle growth, and as a paracrine agent to stimulate spermatogenesis
in the adjacent seminiferous tubules
.
Cell signaling
Cell signaling is part of a complex system of communication that governs basic cellular activities and coordinates cell actions. The ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity as well as normal tissue...
in which the target cell is near ("para" = near) the signal-releasing cell.
Local action
Some signalling 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 factorGrowth factor
A growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation and cellular differentiation. Usually it is a protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes....
and clotting factors are paracrine signalling agents. The local action of growth factor signalling plays an especially important role in the development of tissues. Also, retinoic acid
Retinoic acid
Retinoic acid is a metabolite of vitamin A that mediates the functions of vitamin A required for growth and development. Retinoic acid is required in chordate animals which includes all higher animals from fishes to humans...
, the active form of vitamin A
Vitamin A
Vitamin A is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal, that is necessary for both low-light and color vision...
, functions in a paracrine fashion to regulate gene expression during embryonic development in higher animals. In insects, Allatostatin
Allatostatin
Allatostatins are neuropeptide hormones in insects and crustacea. They have a twofold function: they both inhibit the generation of juvenile hormone and reduce their food intake. They are therefore putative targets for insecticide research....
controls growth though paracrine action on the corpora allata.
In mature organisms, paracrine signalling is involved in responses to allergen
Allergen
An allergen is any substance that can cause an allergy. In technical terms, an allergen is a non-parasitic antigen capable of stimulating a type-I hypersensitivity reaction in atopic individuals....
s, tissue repair, the formation of scar tissue
Scar tissue
Scar tissue can refer to:*Granulation tissue, a product of healing in major wounds*The tissue of a scar*"Scar Tissue", a Red Hot Chili Peppers song*Scar Tissue , the autobiography of Anthony Kiedis, lead singer of the Red Hot Chili Peppers...
, and blood clotting.
Paracrine and endocrine actions
TestosteroneTestosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...
secreted from the testes acts as an endocrine agent to stimulate peripheral events, such as muscle growth, and as a paracrine agent to stimulate spermatogenesis
Spermatogenesis
Spermatogenesis is the process by which male primary germ cells undergo division, and produce a number of cells termed spermatogonia, from which the primary spermatocytes are derived. Each primary spermatocyte divides into two secondary spermatocytes, and each secondary spermatocyte into two...
in the adjacent seminiferous tubules
Seminiferous tubules
Seminiferous tubules are located in the testes, and are the specific location of meiosis, and the subsequent creation of gametes, namely spermatozoa....
.
See also
- Endocrine systemEndocrine systemIn physiology, the endocrine system is a system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body. The endocrine system is in contrast to the exocrine system, which secretes its chemicals using ducts. It derives from the Greek words "endo"...
- Local hormoneLocal hormoneLocal hormones, by one definition, are biologically active polypeptides that are secreted by nerve cells and gland cells and act in a paracrine fashion but also enter the circulation...
- either a paracrine hormone, or a hormone acting in both a paracrine and an endocrine fashion - Paracrine regulatorParacrine regulatorParacrine regulator is a cell of group of cells from the Diffuse Neuro-Endocrine System that produces amines or peptides.External link:*...