The Morphological Study Of Pulmonary Neuroendocrine Cells In Developing Lungs Of Rats

Objective: Pulmonary neuroendocrine cell is a special type of endocrine cell that located in the lung of human and some animals. Nowadays, many sciences are interested in the research of the structure and function of the pulmonary neuroendocrine cell. We hope our research could acquire more morphological evidences about the lung development and the mechanism of the endocrine system in lung. We hope the data that we show in the text could help us to reveal the structure and function of lung.Method: Sixty Sprague Dawlay rats of various ages, breed routinely, were divided into 10 groups according to age randomly. The lung tissue for electron microscopy was cut into section 1mm thick sagittally. The lung tissue for immunohistochemitry and Laser Scanning Confocal Microscopy were fixed and embedded. The morphological alteration of pulmonary neuroendocrine cells which stain for calcitonin gene-related peptide(CGRP), serotonin(S-HT) and luteinizing hormone(LH) were studied. The results of these were dealed with computer image analysis and statistical treatment.Result: 1.Cells contains CGRP firstly appeared in the16-day fetuses. Cells increased in number as gestation progressed and reached its peak at 20-day fetuses. There is significant difference between groups of 16-day and 18-day fetuses. No significant difference was observed between groups of 18-day and 20-day fetuses. The number of CGRP positive cells declined in postnatal rat lungs. A significant difference was seen between groups of 20-day fetuses and 1-day rats and groups of 1-day and 1 week rats. CGRP positive cells in Groups after 7-day rats were very limit and no significant difference in these groups. Most of the CGRP positive cells in 16-day fetuses were round or oval in shape, and usually rest on the basement membrane of epithelium and the primitive alveoli. With the development, these cells could be seen in the epithelium of bronchi, bronchioles and alveolar ducts. 2.Cells secreting 5-HT appeared in 16-day fetuses and most of them rest in the epithelium of the primitive alveoli. Most of these cells were round or oblate in shape and often have a long process. Cells increased in number as gestation progressed and its distribution were widen. There is significant difference between groups of 16-day and 18-day fetuses. No significant difference was observed between groups of 18-day and 20-day fetuses. The number of 5-HT positive cells sharply declined in postnatal rat lungs and a significant difference was seen between groups of 20-day fetuses and 1-day rats. 5-HT positive cells in post in Groups after 1-day rats were very limit and nosignificant difference in these groups. 3.LH positive cells were appeared in 18-day fetuses and rest in the epithelium of bronchioles and the primitive alveoli. The numbers of these cells were very limited and no significant difference was seen in groups. 4.Adjacent sections immunostained with antibodies to CGRP and 5-HT proved the coexistance of CGRP and 5-HT in neuroendocrine cells. 5.The result of electron microscopy shows that some organelles for the secretary action are flourishing in the neuroendocrine cells. There are rich capillary vessels under the basement membrane. 6.The data of Laser Scanning Confocal Microscopy shows that the fluorescence intensity become strong with the development of fetuses and weak in postnatal rat lungs.Conclusion: l.CGRP and 5-HT positive cells changed with the development of the lung and this result suggests that these cells play a important role in the development , differentiation and maturity of the lung. The rapid changes in number during the period of birth may relate with the sharp change in founction of the lung. 3.The result of adjacent sections method proved the coexistance of CGRP and 5-HT in neuroendocrine cells.This finding suggests the possibility of functional interaction of CGRP with 5-HT. 4.LH positive cells were seen in rat lung.