The effect of calcium-regulating hormones on transport of calcium across the chorioallantoic membrane of the chicken embryo.
The hormonal form of vitamin D3 (1,25(OH)2D3), parathyroid hormone (PTH), or appropriate vehicle were injected into the yolk sac of eggs of domestic fowl on days 16 and 17 of incubation. The chorioallantoic membrane (CAM) and overlying inner shell membrane were removed from eggs on day 18 and mounted in a Ussing-type apparatus. Transport of calcium was assessed by monitoring movements of radiolabeled calcium. Transport of calcium from the chorionic aspect of the CAM to the allantoic aspect increased considerably with time for all treatment groups except the one receiving PTH. "Back-flux" of calcium (movement of calcium from the allantoic aspect to the chorionic) was negligible for all treatment groups at all sampling periods. PTH treatment did not affect flux of calcium from allantois to chorion but reduced flux from chorion to allantois considerably. The underlying cause of this effect has not been identified. The hormonal form of vitamin D3 did not affect flux of calcium in either direction. These data raise the possibility that control of calcium transport by the CAM may not be the primary function of the vitamin D hormone.
Packard
M J
MJ
Department of Biology, Colorado State University, Fort Collins 80523-1878, USA. kpackard@lamar.colostate.edu
Clark
N B
NB
Erickson
J P
JP
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002642:Chick Embryo; D002823:Chorion / Q000187:drug effects* / Q000378:metabolism*; D015194:Diffusion Chambers, Culture; D004553:Electric Conductivity; D004847:Epithelial Cells / Q000378:metabolism; D010281:Parathyroid Hormone / Q000494:pharmacology*
D010281:Parathyroid Hormone; D002117:Calcitriol; D002118:Calcium