| Like the alimentary canal, lung is also an endocrine organ. There is a special type of endocrine cells that located in the lung and it has a close relationship with the neuroendocrine system. In 1938, Fieyter detected and named these cells as Clear cell and this is the first step to know pulmonary neuroendocrine cells. As the development of the method of research, the understand of these cells is getting clearer. At the end of 1960's, Pearse et al classified these cells into APUD cell system according to the characteristic of PNEC. At the end of 1980's, Pearse pointed out the diffuse neuroendocrine system also includes the lung. Recently, many scientists are interested in the research of the structure and function of the pulmonary neuroendocrine cell. Scores of active substances in the central and peripheral nervous system were found, e.g. calcitonin-generelated peptide (CGRP), 5-hydroxy-ryptamine (5-HT), substance P (SP) and methionineenkephalin (M-ENK). At the same time, many active substances of peptide and amine were also found in the respiratory tract. They have the functions of motation, sensation, secretion, nutrition, metabolism and protection for the lung, which are recognized as a kind important signal substances interacting between the central nervous system and the lung. These substances are also considered to come from the Non-adrenergic, Non-cholinergic fibers of respiratory tract, named as the third nervous system by some researchers. Recently, some scientists suggested that the self -regulation of the lung is also a key point. More and more researchers are interested in the following questions: whether the lung has the ability of synthesizing and secreting some kinds of peptide; whether there are relationships among these active substances; how these substancesregulate the physiological and pathological process of the lung.Neuropeptide Y (NPY) is one of the most important neurotransmitters and neuroregulators, which is mainly located in the central part of the diffuse neuroendocrine system---hypothalamus. NPY has close relationship with the functions of eating, pressure, pulse rate, respire regulation, the contraction and dilatation of smooth muscle and the regulation of the hypothalamic neuroendocrine function. Also, NPY was found to locate in peripheral organs such as pancreas, and has been confirmed to have the function of vessel contraction. Therefore, our present study focus on answering the following questions: whether NPY is located in the lung; whether NPY could be secreted by the pulmonary endocrine cells; the relationship between NPY and the other active substances; how to complete the regulation of the Q/A.From the reports of the pulmonary endocrine cells, we found the pulmonary endocrine cells are extremely active during the embryogenesis, which is distinct from the normal adult lung tissue. Therefore, the observation of age-related alteration of the NPY, 5-HT, and CGRP expression will help us to understand the genesis and development of the lung completely.Our study used the chromogranin A as the specific marker of the pulmonary neuroendocrine cells, explored the NPY expression in the lung from the process of transcription and translation. And we also observed the relationship among NPY, 5-HT, CGRP, and CgA in the pulmonary neuroendocrine cells. Afterwards, the changes of NPY, 5-HT and CGRP in the developing rat lung were observed with real time. More recent studies indicated that the pulmonary neuroendocrine cells in the pulmonary neuroendocrine cell tumor and in the embryogenesis are similar in some ways. Thereby, we studied the expression of NPY in the pulmonary neuroendocrine cell tumor, in order to offer some valid data to understanding the pathology of the genesis of the pulmonary neuroendocrine cell tumor.Since CgA could combine with the specific hormone, and exists widely in the secreting particles of the pulmonary neuroendocrine cells and theirs tumor. CgA is considered as the specific, sensitive, and reliable marker in the endocrine sys...
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