title: Changes in the concentration of calcitonin in the plasma of chick embryos during incubation.
abstract: Calcitonin (CT) was assayed in the plasma of chick embryos at eight stages of development from  day 17 of incubation to day 1 after hatching by a rat bioassay. The concentration of CT rose steadily from 1060 mu./1 on day 17 to 4700 mu./1 at the stage when pulmonary respiration was initiated on day 20. Nine hours later, when the embryos 'pipped' the shells, the concentration of the hormone more than doubled to reach a peak of 11000 mu./1. At hatching the level had fallen to 1400 mu./1 and 24 h later it was undetectable (less than 500 mu./1). The physiological significance of these changes is discussed in relation to the development of the embryo.
mesh_terms: D000818:Animals; D001681:Biological Assay; D002116:Calcitonin / Q000097:blood*; D002118:Calcium / Q000097:blood; D002642:Chick Embryo / Q000502:physiology*; D005260:Female; D051381:Rats
chemical_list: D002116:Calcitonin; D002118:Calcium