HAMSTER PULMONARY ENDOCRINE-CELLS WITH POSITIVE IMMUNOSTAINING FOR CALBINDIN-D-28K

We have examined the distribution of calcium-binding proteins (CaBPs) in adult and fetal lungs of Syrian golden hamsters (Mesocricetus aurat us) using immunostaining with confocal laser microscopy and electron m icroscopy. Single and grouped (neuroepithelial body; NEB) endocrine ce lls were distributed from bronchi to alveolar ducts in the adult lung. Serial frozen sections immunostained for CaBPs in combination with im munostaining for endocrine markers such as calcitonin gene-related pep tide, serotonin, PGP9.5, and synaptophysin revealed that positive immu nostaining for calbindin-D-28K (CB-D28K) was seen in single endocrine cells and NEBs. However, other so-called EF-hand family CaBPs, parvalb umin and calretinin, were not detected. Electron microscopically, posi tive immunoreaction for CB-D28K was mainly in the organelle-free cytop lasmic matrix of endocrine cells, and partly in nuclei and associated with secretory granules and endoplasmic reticulum. In fetal developing lungs, endocrine cells appeared first on gestational day 13, and they were positive for all the endocrine markers used. However, pulmonary endocrine cells were positively immunostained for CB-D28K from gestati onal days 15 and 16 onward. In summary, our observations suggest that CB-D28K is a useful marker for endocrine cells of the lung, and CB-D28 K could function as a mediator of endocrine stimulation or calcium hom eostasis in pulmonary endocrine cells.