Influence of calcium and vitamin D deficient diet on calcitonin gene expression in the ultimobranchial cells of the developing chicken
1993
Elian-Cisse, M.C. | Taboulet, J. | Bielakoff, J. | Lasmoles, F. | Vernejoul, M.C. de | Treilhou-Lahille, F.
Recently hatched chickens were fed a vitamin D and calcium deficient diet for 4 weeks. Calcitonin (CT) biosynthesis in the ultimobranchial glands (UBG) was studied during the treatment by means of in situ hybridization of specific CT mRNAs and immunocytochemical detection of the CT intracellular stores. Circulating CT levels were measured by radioimmunoassay. Within 1 week of the start of treatment, the deficient animals had significantly lowered plasma calcium concentrations and a dramatic fall of plasma CT levels, but the UBGs were not much affected. From week 2 to week 4, the UBG underwent a gradual atrophy. The tissue became lacunar due to the presence of an abnormally developed cystic component. Although calcemia returned to normal at week 4, the cellular endocrine cords were dramatically reduced, corresponding to the undetectable circulating CT levels. However, the UB glands always contained persistant CT-secreting cells, mainly at the periphery of the tissue or in contact with enlarged parathyroid tissue inclusions. These endocrine UB cells contained large amounts of hybridizable CT mRNA and immunodetectable stores of the mature hormone, and their ultrastructural features were quite unaffected compared to normal ones. Thus, we conclude that, in the chicken, severe calcium malnutrition led to a striking reduction of CT biosynthesis in the UB glands by decreasing the number of secretory cells and not by triggering modifications of the biosynthetic activity of the UB endocrine cells.
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