IMMUNOREACTIVE LUTEINIZING-HORMONE (IR-LH) CELLS IN THE LUNG AND STOMACH OF CHICK-EMBRYOS

Luteinizing hormone (LH) immunoreactivity was detected in the lung and stomach of chick embryos by the immunoperoxidase staining technique u sing specific antiserum to chicken LH. Immunoreactive LH (ir-LH) cells first appeared in the primordial cells of the epithelial layer of lun g bud and foregut as well as of Rathke's pouch in the 3-day-old embryo , Hamburger and Hamilton stage 21. Ir-LH cells increased in number wit h advancing age of embryos in the lung, stomach, and pituitary gland. In the lung of 7-day-old embryos, stage 31, the ir-LH cells were distr ibuted in the epithelium of primary, secondary, and tertiary bronchi, and their shapes were pseudostratified columnar, simple columnar, and simple cuboidal, depending on their sites in the intrapulmonary airway . Ir-LH cells were more numerous in the median part than in the latera l part of the lung, and the population in the epithelial layer of ento bronchi of the secondary bronchi was 4 times higher than that in ectob ronchi and laterobronchi of the secondary bronchi and in the primary b ronchi. The immunoreactive products were found, either in the entire c ell or in the apical part, facing the lumina of bronchi. In the stomac h, ir-LH cells were found in the epithelial layer of gastric glands. N o ir-LH cells were observed in interstitial regions, which consisted o f mesenchymal cells and blood vessels, in the lung and stomach tissues . With advancing age, ir-LH cells changed their shapes to flat or squa mous, coincident with the formation of parabronchi. Other pituitary ho rmones were not observed immunohistochemically in either the lung or s tomach before hatching. Preabsorption of the antiserum against avian L H with the purified chicken LH or the extract of pituitaries from 10-d ay-old embryos completely destroyed the immunoreactivity to the cells in the lung and the pituitary. A single band of the immunoreaction pro ducts, whose molecular weight was around 25 K daltons, was shown by th e immunostaining of nitrocellulose membrane transblotted after sodium dodecylsulphate-polyacrylamide gel electrophoresis of the purified pit uitary LH, extracts of pituitaries from 10-day-old embryos, and the ex tracts of lungs from 7-, 10-, and 14-day-old chick embryos. These resu lts demonstrated that ir-LH cells are present in extrapituitary tissue s, and may play an important role during the development of chick embr yonic lung and stomach.