MECHANISM OF CALCIUM SECRETION IN AVIAN SHELL GLAND (UTERUS)
MECHANISM OF CALCIUM SECRETION IN AVIAN SHELL GLAND (UTERUS)
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DOI：
10.1095/biolreprod19.3.505
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发表时间：
1978-01-01
影响因子：
3.6
通讯作者：
SPAZIANI, E
中科院分区：
文献类型：
--
作者：
EASTIN, WC;SPAZIANI, E
探讨了鸟类壳腺（SG）运输大量Ca（和HCO 3）组装蛋壳的机制。实验在原位灌注的SG中进行。除非另有说明，否则母鸡在选择使用时会分泌壳（活性）。与输卵管的另一部分--枕大肌相比，SG的细胞外室更大，Ca分布在更大的总体积中，其中大部分是细胞外的。Ca在两个器官中的细胞内分布相似。SG中的含水量和维管空间/g总是较大的，并且当蛋壳形成时，SG维管空间增加40%。循环中的放射性钙以密切反映血液中钙清除率的速率迅速出现在SG管腔中。循环菊糖-14 C也出现在管腔中的显着数量，虽然在较低的速度比钙。菊糖渗透率的管腔是4倍，在活跃的比在非活跃的SG。总的来说，这些观察结果是一致的存在于SG的高渗透性，细胞旁分流途径的被动通量，这些路径变得更具渗透性在壳形成。用生理平衡的离子溶液灌注SG腔表明，Ca、HCO 3和K通常被分泌，而Na和Cl被吸收。由于人为改变灌注的Ca浓度，在没有灌注Ca的情况下，Ca的分泌略高，但在相当大的血浆：腔Ca浓度梯度的情况下，分泌继续以恒定速率进行。此外，增加Ca浓度倾向于增加HCO 3分泌。增加灌注HCO 3增加Ca分泌，而急剧降低HCO 3分泌，这样在高浓度时，HCO 3发生净吸收。乙酰唑胺可逆地取消钙和HCO 3分泌，而只有轻微影响钠和氯的吸收。提高灌流钠增加钙分泌和急剧增加钠吸收。哇巴因使Na和Cl的吸收变为分泌，而仅使Ca和HCO_3的分泌抑制60%。哇宾的作用是完全可逆的。净水通量的内腔，诱导增加管腔渗透压与非电解质添加到通常的盐，抑制Na和Cl的吸收，而略有增加HCO 3的分泌。在离子实验中测量时，跨壁电位差很小（10-16 mV），没有显著变化，有利于阳离子转运到管腔。K分泌不受任何操纵的管腔环境。钙的分泌既通过扩散发生，更重要的是通过主动转运发生。净钙分泌似乎并不严重依赖于钠的吸收。钙分泌似乎在功能上与管腔HCO 3浓度和HCO 3产生有关。HCO 3的分泌比Ca的分泌更多地取决于浓度梯度，但HCO 3也是主动转运的。
The mechanism by which the avian shell gland (SG) transports large amounts of Ca (and HCO3) for assembly of an eggshell was explored. Experiments were conducted in SGs perfused in situ. Unless otherwise stated, hens were secreting shell (active) when selected for use. Compared with another part of the oviduct, the magnum, the SG extracellular compartment is greater and Ca is distributed in a larger total volume of which most is extracellular. Intracellular distribution of Ca is similar in the 2 organs. Water content and vascular space/g is always larger in the SG and, when an eggshell is forming, SG vascular space increases 40%. Radioactive Ca in the circulation rapidly appears in the SG lumen at rates closely reflecting Ca clearance in the blood. Circulating inulin-14C also appears in the lumen in significant quantities, although at slower rates than Ca. Inulin penetration rate to the lumen was 4-fold higher in active than in inactive SG. Collectively, these observations are consistent with the presence in the SG of highly permeable, paracellular shunt pathways for passive fluxes and that these paths become more permeable during shell formation. Perfusion of the SG lumen with physiologically balanced ionic solution showed that Ca, HCO3 and K normally are secreted, while Na and Cl are absorbed. As the perfused Ca concentration was varied artificially, Ca secretion was somewhat higher in the absence of perfused Ca, but secretion continued at constant rate against a considerable plasma:lumen concentration gradient of Ca. Also, increasing the Ca concentration tended to increase HCO3 secretion. Increasing perfused HCO3 raised Ca secretion while sharply lowering HCO3 secretion such that at high concentration, net absorption of HCO3 occurred. Acetazolamide reversibly abolished Ca and HCO3 secretions while only slightly affecting Na and Cl absorption. Raising perfused Na increased Ca secretion and sharply increased Na absorption. Ouabain changed Na and Cl absorption to secretion, while only depressing Ca and HCO3 secretion 60%. Effects of ouabin were completely reversible. Net water flux to the lumen, induced by increasing luminal osmotic pressure with a nonelectrolyte added to the usual salts, depressed Na and Cl absorptions while slightly increasing HCO3 secretion. Where measured in the ion experiments, the transmural electrical potential difference was small (10-16 mV), did not change significantly and favored cation transport to the lumen. K secretion was not affected by any manipulation of the luminal environment. Ca secretion occurs both by diffusion and, more importantly, by active transport. Net Ca secretion does not appear to be critically dependent upon Na absorption. Ca secretion does appear to be linked functionally to luminal HCO3 concentration and upon HCO3 production. HCO3 secretion depends more upon a concentration gradient than does Ca secretion, but HCO3 is also actively transported.