Editing Neuroendocrine cell (section)

== Pulmonary neuroendocrine cells ==
'''Pulmonary neuroendocrine cells''' ('''PNECs''') are specialized airway [[epithelial cells]] that occur as solitary cells or as clusters called neuroepithelial bodies (NEBs) in the [[lung]]. Pulmonary neuroendocrine cells are also known as ''bronchial'' [[Kulchitsky cell]]s.<ref name="French">{{Cite journal|title=Neuroendocrine differentiation in lung carcinoma |author=Addis, B. J. |journal=Thorax |date=1995 |volume=50|issue=2|pages=113–115 |doi=10.1136/thx.50.2.113 |pmid=7701446 |pmc=473889}}</ref> They are located in the [[respiratory epithelium]] of the upper and lower [[respiratory tract]]. PNECs and NEBs exist from [[fetus|fetal]] and neonatal stages in the lung airways.

These cells are bottle- or flask-like in shape, and reach from the [[basement membrane]] to the [[lumen (anatomy)|lumen]]. They can be distinguished by their profile of bioactive amines and peptides, namely [[serotonin]], [[calcitonin]], [[calcitonin gene-related peptide]] (CGRP), [[chromogranin A]], [[gastrin-releasing peptide]] (GRP), and [[cholecystokinin]].

These cells can be the source of several types of lung cancer, most notably small cell carcinoma of the lung, and bronchial carcinoid tumor.<ref>{{cite journal |vauthors=Chong S, Lee KS, Chung MJ, Han J, Kwon OJ, Kim TS |title=Neuroendocrine tumors of the lung: clinical, pathologic, and imaging findings |journal=Radiographics |volume=26 |issue=1 |pages=41–57; discussion 57–8 |year=2006 |pmid=16418242 |doi=10.1148/rg.261055057}}</ref><ref name="Becker">{{cite journal |last1=Becker |first1=KL |last2=Silva |first2=OL |title=Hypothesis: the bronchial Kulchitsky (K) cell as a source of humoral biologic activity. |journal=Medical Hypotheses |date=July 1981 |volume=7 |issue=7 |pages=943–9 |doi=10.1016/0306-9877(81)90049-9 |pmid=6270516}}</ref>

=== Function ===
PNECs may play a role with chemoreceptors in [[hypoxia (medical)|hypoxia]] detection. This is best supported by the presence of an oxygen-sensitive potassium channel coupled to an oxygen sensory protein in the rabbit lumenal membrane. They are hypothetically involved in regulating localized epithelial cell growth and regeneration through a [[Paracrine signalling|paracrine mechanism]], whereby their signaling peptides are released into the environment.  In addition, they contain neuroactive substances which are released from basal cytoplasm. These substances induce autonomic nerve terminals or vasculature in the deep [[lamina propria]].

=== Role in fetal lung ===
In the fetal lung, they are frequently located at the branching points of airway tubules, and in humans are present by 10 weeks gestation. Peptides and amines released by PNEC are involved in normal fetal lung development including branching morphogenesis. The best-characterized peptides are GRP, the mammalian form of bombesin, and CGRP; these substances exert direct mitogenic effects on epithelial cells and exhibit many properties akin to growth factors.