Development of calcium reabsorption by the allantoic epithelium in chick embryos grown in shell-less culture.
The allantoic sac of the chick embryo functions as a primitive urinary bladder, storing and modifying the excretory fluid produced by the embryo. We have used chick embryos grown in shell-less culture to study the in situ handling of Ca2+ by the allantoic epithelium. Between Days 8 and 13 of incubation (38 degrees C, 5% CO2), the [Ca2+] of the allantoic sac fluid declines from about 1.5 mM to less than 0.3 mM, with most of this Ca2+ reabsorption occurring between Days 10 and 11. In 13-day-old embryos, the allantoic epithelium reabsorbs within 24 hr 85-92% of 45Ca2+ injected into the allantoic sac, while in 9-day-old embryos 45Ca2+ reabsorption is less than 40% by 24 hr. This is evidence for the developmental onset of a Ca2+ reabsorption process in the allantoic epithelium. The allantoic fluid Ca2+ is reabsorbed into the embryo's blood in which the serum [Ca2+] is about 1.5 mM. Also, electrical potential profiles reveal that the serosal (mesenchymal) side of the allantoic epithelium is 15-30 mV positive compared to the mucosal (luminal) side. Thus, by electrochemical criteria this reabsorption process appears to be active.
D000042:Absorption; D000482:Allantois / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002642:Chick Embryo / Q000502:physiology*; D046508:Culture Techniques; D004528:Egg Shell; D004848:Epithelium / Q000378:metabolism; D005321:Extraembryonic Membranes / Q000378:metabolism*; D008564:Membrane Potentials; D013997:Time Factors
D002118:Calcium