Graves J S, Helms E L, Martin H F
Dev Biol. 1984 Feb;101(2):522-6. doi: 10.1016/0012-1606(84)90166-0.
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.
鸡胚的尿囊起着原始膀胱的作用，储存并改变胚胎产生的排泄液。我们利用在无壳培养中生长的鸡胚来研究尿囊上皮对钙离子（Ca2+）的原位处理。在孵化的第8天至第13天（38摄氏度，5%二氧化碳）之间，尿囊液中的钙离子浓度从约1.5毫摩尔/升降至低于0.3毫摩尔/升，大部分钙离子重吸收发生在第10天至第11天之间。在13日龄的胚胎中，尿囊上皮在24小时内重吸收注入尿囊的45Ca2+的85% - 92%，而在9日龄的胚胎中，24小时内45Ca2+的重吸收少于40%。这证明了尿囊上皮中钙离子重吸收过程的发育起始。尿囊液中的钙离子被重吸收进入胚胎血液，其中血清钙离子浓度约为1.5毫摩尔/升。此外，电位分布图显示，尿囊上皮的浆膜（间充质）侧相对于黏膜（管腔）侧呈15 - 30毫伏的正电位。因此，根据电化学标准，这个重吸收过程似乎是主动的。
