Protein restriction sequentially induces new urea transport processes in rat initial IMCD.
Protein restriction sequentially induces new urea transport processes in rat initial IMCD.
复制标题
蛋白质限制依次诱导大鼠初始 IMCD 中新的尿素转运过程。
DOI：
10.1152/ajprenal.1994.266.5.f756
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Sands,JM
中科院分区：
文献类型：
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作者：
Isozaki,T;Gillin,AG;Swanson,CE;Sands,JM
我们报道给大鼠喂食 8% 蛋白质 4 周，在初始内髓集合管 (IMCD) 中诱导两个新的尿素转运过程；在喂食 18% 蛋白质的老鼠中，这两种物质都不存在。在这项研究中，我们测量了在喂食 8% 蛋白质的大鼠的灌注初始 IMCD 片段中诱导这些转运蛋白的时间过程。 3周后诱导净尿素通量，而2周后诱导加压素刺激的被动尿素渗透性（P（尿素））。 8-溴腺苷3',5'-环单磷酸（8-BrcAMP）显着增加P（尿素））；添加加压素不会进一步增加 P（尿素）。事实上，饲喂 18% 或 8% 蛋白质的大鼠的初始或终末 IMCD 片段中加压素刺激的 cAMP 产生没有差异，这表明适应性反应不是由于 cAMP 产生增加所致。胰高血糖素不会改变 cAMP 的产生或 P（尿素）。由于饲喂 8% 蛋白质，醛糖还原酶和山梨糖醇脱氢酶活性均未发生变化，因此表明了该反应的特异性。因此 1) 在初始 IMCD 片段中，2 周后诱导加压素刺激的 P(尿素)，但净尿素通量需要 3 周饲喂 8% 蛋白质； 2) 这种适应不仅仅归因于更高的 cAMP 产生率； 3) 由于对集中能力下降作出反应的酶活性没有改变，因此表明了适应性反应的特异性。这些结果表明两种不同的尿素转运蛋白可能参与低蛋白饮食的适应。
We reported that feeding rats 8% protein for 4 wk induces two new urea transport processes in initial inner medullary collecting ducts (IMCD); neither is present in rats fed 18% protein. In this study, we measured the time course of induction of these transporters in perfused initial IMCD segments from rats fed 8% protein. Net urea flux was induced after 3 wk, whereas vasopressin-stimulated passive urea permeability (P(urea)) was induced after 2 wk. 8-Bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) significantly increased P(urea)); adding vasopressin did not increase P(urea) further. In fact, there was no difference in vasopressin-stimulated cAMP production in initial or terminal IMCD segments from rats fed 18% or 8% protein, suggesting that the adaptive response was not due to increased cAMP production. Glucagon did not change cAMP production or P(urea). Specificity of the response was suggested because neither aldose reductase nor sorbitol dehydrogenase activity changed with feeding 8% protein. Thus 1) in initial IMCD segments, vasopressin-stimulated P(urea) is induced after 2 wk, but net urea flux requires 3 wk of feeding 8% protein; 2) this adaptation is not solely due to a higher rate of cAMP production; and 3) specificity of the adaptive response is suggested because activities of enzymes responding to decreases in concentrating ability are unchanged. These results suggest that two distinct urea transporters may be involved in the adaptation to a low-protein diet.