Bombesin may play a role in fetal lung growth and maturation in utero and in lung organ culture.

21S Gly-Asp)-containing peptides inhibited branching of lung rudiments, which suggested involvement of integrin extracellular matrix receptors.t Incubation of li-d-old lung rudiments in the presence of exogenous FN resulted in impairment Of lung branching (14 new branching points, compared to more than 20 in controls). Moreover, dissociated cells from 11and 13-d embryos attached and spread on FN and express a5 l FN receptors. However, neither the 120-kD FN fragment containing the RGD sequence nor antibodies to this adhesive site in FN affected lung development in vitro (26 branching points). The 65175 kD carboxyterminal fragment of FN contains the IIICS adhesive site and did not have an effect on branching (35 branching points). In contrast, incubation of the 70-kD aminoterminal FN fragment resulted in significant inhibition of normal in vitro lung development (11 branching points). The 70-kD aminoterminal FN fragment inhibited deposition of FN matrices of cultured fibroblasts. These findings suggest that FN matrix assembly is critical for in vitro lung development. Work is currently underway to isolate the FN aminoterminal domain “receptor” critical for normal lung development and presumably for wound healing.