NCAM expression in the pulmonary neural and diffuse neuroendocrine cell system

Neural cell adhesion molecule (NCAM)--a membrane protein involved in cell-cell adhesion within the central and peripheral nervous systems--was demonstrated to be a sensitive and specific marker for neuroepithelial bodies (NEB) and neural tissue elements in the cat lung. Using the streptavidin-biotin immunoperoxidase method, NCAM reactive sites were investigated with monoclonal and polyclonal antibodies on serial section of Bouin fixed, paraffin embedded lung tissue. Moreover, NCAM expression was compared with that of neuron-specific enolase (NSE) on adjacent sections. The most obvious NCAM staining was obtained with the monoclonal antibody. From newborn to adult life, cell surface labeling was identified on NEB cells. In mature cat lung, they were no longer positive. Solitary neuroendocrine cells (NEC) were always negative. In contrast to the transient postnatal immunoreactivity of NEB cells, nerve fibers and ganglion cells were stained throughout all life stages and studied. The distribution of NCAM in NEB, nerve fibers and ganglion cells was similar to that NSE, except in the adult lung. This study reveals that during lung growth shared NCAM antigens exist between the pulmonary nervous and endocrine system, whereas in mature lung NCAM proteins are confined to neural tissue elements. The difference in NCAM expression between NEB and NEC might suggest an involvement of NCAM in the formation of contacts between NEB cells and nerves.