Water transport in collecting ducts of Japanese quail.
Water transport in collecting ducts of Japanese quail.
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日本鹌鹑集水管中的水输送。
DOI：
10.1152/ajpregu.1996.271.6.r1535
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Patel,TB
中科院分区：
文献类型：
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作者：
Nishimura,H;Koseki,C;Patel,TB
以前，我们报告说，逆流尿液浓缩机制在鸟类似乎是通过循环的单一溶质（氯化钠），其中厚的上升肢体环状肾单位提供了一个能源。为了确定髓集合管（MCD）在逆流倍增系统的重要性，我们研究了在隔离和灌注的MCDs从日本鹌鹑，鹌鹑，渗透和/或扩散水渗透性和精氨酸催产素（AVT）是否调节水渗透性。我们注意到，在皮质集合管（CD）中存在具有电子致密细胞质和大量线粒体的暗细胞和亮粘液分泌细胞，而MCDs中仅存在粘液分泌细胞。完整鸟类和缺水鸟类MCDs的体积通量（Jv）几乎为零;暴露于高渗浴和AVT（2 × 10（-5）M）后，缺水鸟类的Jv显著较高。浸泡在等渗浴中的MCDs的扩散水渗透性（Pdw）中等偏高，其中AVT（10（-5）M，浴）略微增加Pdw，毛喉素（Fsk）更显著（10（-5）M），而1，9-双脱氧Fsk（一种无活性类似物）显示无影响。此外，髓质中的基础环磷酸腺苷（cAMP）水平高于皮质中的cAMP水平，皮质和髓质中的cAMP水平仅被AVT（10（-5）M）轻微刺激，而被Fsk（10（-4）M）显著刺激。这些结果在C. coturnix CD显示以下内容。1)存在两种类型的细胞;而暗细胞在形态上类似于哺乳动物的闰细胞，但不确定分泌粘液的细胞是否等同于主细胞。2)AVT通过cAMP机制增加Pdw;然而，相对较高的基础Pdw和AVT对Jv和Pdw的轻微影响表明，可能会发生跨越MCD的扩散水运动，而不受AVT的直接控制。
Previously, we reported that the countercurrent urine concentration mechanism in birds appears to operate by recycling of a single solute (NaCl), in which the thick ascending limb of looped nephrons provides an energy source. To determine the importance of the medullary collecting duct (MCD) in the countercurrent multiplier system, we examined in isolated and perfused MCDs from Japanese quail, Coturnix coturnix, the osmotic and/or diffusional water permeability and whether arginine vasotocin (AVT) regulates water permeability. We noted that dark cells that possess electron-dense cytoplasm and numerous mitochondria and light mucus-secreting cells exist in the cortical collecting duct (CD), whereas only mucus-secreting cells are present in the MCDs. The volume flux (Jv) in the MCDs from intact birds and that from the water-deprived birds were nearly zero; after exposure to a hyperosmotic bath and AVT (2 x 10(-5) M), the Jv was significantly higher in water-deprived birds. The diffusional water permeability (Pdw) was moderately high in MCDs bathed in an isosmotic bath in which the Pdw was increased slightly by AVT (10(-5) M, bath) and more markedly (10(-5) M) by forskolin (Fsk), whereas 1,9-dideoxy Fsk (an inactive analogue) showed no effect. Furthermore, the basal adenosine 3',5'-cyclic monophosphate (cAMP) levels were higher in the medulla than in the cortex and were stimulated only slightly by AVT (10(-5) M) and markedly by Fsk (10(-4) M) in both the cortex and medulla. These results in the C. coturnix CD indicate the following. 1) Two types of cells are present; whereas dark cells resemble mammalian intercalated cells morphologically, it is not certain whether mucus-secreting cells are equivalent to principal cells. 2) AVT increases Pdw via a cAMP mechanism; the relatively high basal Pdw and minor effect of AVT on Jv and Pdw suggest, however, that diffusional water movement across the MCD may occur without significant direct control by AVT.