Ontogeny of Corticosterone-Inducible Growth Hormone-Secreting Cells during Chick Embryonic Development

Abstract

We reported that corticosterone administration into the albumen of fertile chicken eggs on embryonic day (e) 11 induces an increase in the population of GH-secreting cells. The present study evaluated the ontogeny, dose response, localization, and persistence of the glucocorticoid-induced increase in the somatotroph population during chicken embryonic development. Corticosterone (0, 0.02, 0.2, and 2 μg in 300 μl saline) was injected into separate eggs on e9, e10, e11, and e12, and the population of GH-secreting cells was assessed 2 days later using reverse hemolytic plaque assays. Corticosterone treatment on e9 or e10 was unable to increase the population of GH-secreting cells on e11 or e12. In contrast, 0.2 and 2 μg of corticosterone on e11 increased the population of GH-secreting cells on e13 (P < 0.05, n = 3 experiments) to 8.2 ± 0.6 and 6.4 ± 0.5% of all cells, respectively, relative to controls (2.4 ± 0.2%). For e14 embryos treated on e12, only the 2 μg dose increased the proportion of GH-secreting cells (6.4 ± 0.6%) relative to controls (3.6 ± 0.4%). In a second experiment, 0, 0.02, 0.2, 2, and 20 μg of corticosterone were injected on e0, e8, e9, e10, e11, and e12, and the population of