Yasuda G, Jeffries W B
Second Department of Internal Medicine, Yokohama City University School of Medicine, Japan.
Kidney Int. 1998 Jul;54(1):80-6. doi: 10.1046/j.1523-1755.1998.00990.x.
The inner medullary collecting duct (IMCD) is composed of at least two functionally and morphologically distinct segments, the initial (IMCDi) and the terminal (IMCDt) portions. However, most studies of receptor signaling have been performed on cells obtained from the entire inner medulla. The purpose of this study was to determine whether the patterns of receptor-activated cAMP accumulation were different between these segments.
We measured cAMP accumulation stimulated by vasopressin and isoproterenol, and the effect of epinephrine in freshly dissected IMCDi and IMCDt segments cultured and IMCDi and IMCDt cells in primary culture.
The maximum response to vasopressin was twofold higher in fresh IMCDt verus IMCDi (P < 0.05), however, it increased in cultured IMCDi by 40% verus fresh cells with no change in the response in fresh verus cultured IMCDt. The maximum response to isoproterenol was small in fresh cells but increased by five- and sixfold, respectively, in cultured IMCDi and IMCDt cells. alpha 2-Adrenoceptor stimulation almost completely inhibited both vasopressin and isoproterenol-stimulated cAMP accumulations in fresh IMCDi and IMCDt cells, but only partially inhibited either accumulation by 34 to 49% in cultured cells.
(1) IMCDi and IMCDt cells are both subject to vasopressin and alpha 2- and beta-adrenergic regulation of adenylyl cyclase activity; (2) the relative influence of beta-adrenergic, alpha 2-adrenergic and V2 receptors to affect cAMP accumulation is altered in primary culture versus freshly dissected IMCD segments, suggesting that caution must be exercised in the extrapolation of data from cultured IMCD cells to in vivo models.
髓质内集合管（IMCD）由至少两个功能和形态不同的节段组成，即起始部（IMCDi）和终末部（IMCDt）。然而，大多数受体信号传导研究是在从整个髓质获得的细胞上进行的。本研究的目的是确定这些节段之间受体激活的环磷酸腺苷（cAMP）积累模式是否不同。
我们测量了血管加压素和异丙肾上腺素刺激的cAMP积累，以及肾上腺素对新鲜分离的培养IMCDi和IMCDt节段以及原代培养的IMCDi和IMCDt细胞的影响。
新鲜IMCDt对血管加压素的最大反应比IMCDi高两倍（P < 0.05），然而，培养的IMCDi中其反应比新鲜细胞增加了40%，而新鲜与培养的IMCDt中的反应没有变化。新鲜细胞对异丙肾上腺素的最大反应较小，但在培养的IMCDi和IMCDt细胞中分别增加了五倍和六倍。α2-肾上腺素能受体刺激几乎完全抑制了新鲜IMCDi和IMCDt细胞中血管加压素和异丙肾上腺素刺激的cAMP积累，但在培养细胞中仅部分抑制了其中任何一种积累，抑制率为34%至49%。
（1）IMCDi和IMCDt细胞均受血管加压素以及α2-和β-肾上腺素能对腺苷酸环化酶活性的调节；（2）与新鲜分离的IMCD节段相比，原代培养中β-肾上腺素能、α2-肾上腺素能和V2受体对cAMP积累的相对影响发生了改变，这表明在将培养的IMCD细胞数据外推到体内模型时必须谨慎。
