Accelerating and Retarding Effects of Dexamethasone on the Development of the Avian Lung

Abstract

Fertile eggs from Bovans hybrid were treated with dexamethasone on day 17 of incubation. This treatment resulted in a stimulation of the surfactant synthesis as recorded by the increased uptake of 14C-choline into the pulmonary phosphatidylcholine and the accumulation of lipoid vacuoles. On the other hand, dexamethasone caused a delay in pulmonary fluid absorption till day 19. This delay seems to be caused by a retarded onset of lung circulation. This conclusion has been derived from the lowered pulmonary hemoglobin content at this developmental stage. On the basis of the activities of ornithokallikrein and the angiotensin converting enzyme, ornithokinin may be involved in the retarded onset of circulation.

Dexamethasone and epinephrine stimulate surfactant secretion in type II cells of embryonic chickens

“…The administration of corticosterone to intact embryos stimulates disaturated PC synthesis in the lungs of day 18 chickens (25). In addition, the treatment of chicken eggs with dexamethasone on day 17 of incubation results in a stimulation of PS synthesis in the embryo at days 18 and 19 (53). In this study, PC secretion from type II cells was enhanced by glucocorticoids only when the cells were cocultured with fibroblasts.…”

“…However, in cell cultures of day 20 chick embryos and of hatchlings, dexamethasone had no effect on PC secretion, despite the fact that fibroblasts and type II cells were in direct contact. Furthermore, dexamethasone increases choline incorporation into PC at days 18 and 19, but not on day 20 of incubation (53). Mature rat type II cells secrete a factor that inhibits fibroblast function and therefore the glucocorticoid response (1).…”

“…Glucocorticoids have been found to increase surfactant phospholipid synthesis, secretion, and lipid saturation (20) and are believed to mediate their effects on type II cells through interstitial fibroblasts (42). Although there is some evidence to suggest that glucocorticoids contribute to avian surfactant maturation (25,46,53), the mechanism remains unclear, in particular whether glucocorticoids will promote secretion of PS from type II cells via a pathway involving fibroblasts.…”

Inhibition of glucocorticoid-induced cataracts in chick embryos by RU486: A model for studies on the role of glucocorticoids in development

“…Namely, these concern retina formation ( Koehler and Moscona, 1975), alkaline phosphatase levels of duodenal epithelium (Moog and Richardson, 1955) and production of surfactants in lung (Hylka and Doneen, 1983;Wittmann et al, 1989;Sullivan and Orgeig, 2001). These responses were measured after GC administration in ovo and/or in isolated tissues in vitro.…”

Hypoxic control of the development of the surfactant system in the chicken: evidence for physiological heterokairy

“…The synthetic glucocorticoid dexamethasone (Dex) applied in vitro enhances PL synthesis and secretion from cultured embryonic chicken type II cells (25). Moreover, in ovo administration of glucocorticoids and thyroid hormones to chicken eggs and embryos can accelerate overall lung development, with increased synthesis and secretion of total lung PL (6,11,31,32).…”