ENDOTHELIN IN NORMAL LUNG-TISSUE OF NEWBORN MAMMALS - IMMUNOCYTOCHEMICAL DISTRIBUTION AND COLOCALIZATION WITH SEROTONIN AND CALCITONIN-GENE-RELATED PEPTIDE

We demonstrated immunoreactivity for endothelins (ET)-1, -2, and -3 an d for the precursor, big-ET-1, in the pulmonary diffuse neuroendocrine system (PDNES) of newborn cat, rat, hamster, and mouse. ET-like posit ive neuroepithelial bodies (NEB) were numerous in the intrapulmonary a irways and the alveolar parenchyma. Single neuroendocrine cells (NEC) were less often labeled and mainly localized in the larger bronchi. ET -3-reactive neuronal elements were rarely observed. The intensity and number of immunostained NEB were highest for ET-3, followed in declini ng order by big-ET-1, ET-1, and ET-2. ET-like possessing NEB displayed interspecies differences. We conclude that ET-3 represents a neuroend ocrine form of the ET peptide family. NEB expressing several ET isofor ms can be grouped into NEB containing either big-ET-1 and ET-1 or ET-3 only. ET-like immunoreactivity was present in a subpopulation of sero tonin (5HT)- and/or calcitonin gene-related peptide (CGRP)-positive NE B. As ET, 5HT, and CGRP have potent pulmonary vaso- and /or bronchomot or effects, our observations suggest that they play a separate or syne rgistic role in regulatory function of the mammalian PDNES, exerting t heir influence by paracrine, endocrine, and neurocrine pathways or a c ombination of these.