AN ONTOGENIC STUDY ON ENDOTHELIN-PRODUCING CELLS IN THE RAT LUNG AND SUBMANDIBULAR-GLAND

We ontogenetically examined endothelin (ET) in the lungs and submandib ular glands of Wistar rats at various stages, from fetuses to the aged , using specific polyclonal ET-antibody. In the lung, strong ET-immuno positive cells first appeared at 13 days of gestation in the bronchial epithelia, and the strongest immunoreactivity at 17 days; thereafter, the reactivity gradually decreased, disappearing after birth. However , the gene expression of ET-1, ET-3, the receptor A (ET-AR), and B (ET -BR) was observed continuously throughout all the stages. In the subma ndibular glands, ET-immunopositive cells were first observed in the du ct cells at 18 days of gestation; these cells gradually increased in n umber after birth. In the adult rat, the immunoreactivity was confined predominantly to the granular convoluted tubule. This reactivity was found in every age group, including the aged (3-year-old) rats. All th e gene expression of ET-1, ET-3, ET-AR, and ET-BR was observed in the submandibular glands of postnatal and adult rats. We speculate that th e ET in these tissues may possibly act as a growth factor.