Transport of guanidine in rabbit intestinal brush-border membrane vesicles.
Transport of guanidine in rabbit intestinal brush-border membrane vesicles.
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兔肠刷状缘膜囊泡中胍的转运。
DOI：
10.1152/ajpgi.1988.255.1.g85
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Leibach,FH
中科院分区：
文献类型：
--
作者：
Miyamoto,Y;Ganapathy,V;Leibach,FH
本文研究了离体兔近端小肠刷状缘膜囊对胍的摄取特性。胍的摄取是许多倍更大的存在下向外定向的H+梯度（细胞内pH = 5.5;细胞外pH = 7.2）比在没有H+梯度（细胞内和细胞外pH = 7.2）。胍吸收的时间过程中表现出的H+梯度的存在下，过冲现象，表明发生上坡运输。这种H+梯度刺激的胍摄取不是由于内部负H+扩散电位，因为羰基氰4-三氟甲氧基苯腙，质子载体，未能对胍摄取有任何影响。此外，瞬态上坡运输胍观察到，即使在电压钳位膜囊泡。然而，在有效消散H+梯度的条件下，没有胍的主动运输。胍的这种H+梯度依赖性转运机制与Na+-H+交换剂不同，因为阿米洛利即使在高达100 μ M的浓度下也不抑制胍的摄取。这些数据提供了证据的胍-H+反向转运系统的存在下，在兔肠刷状缘膜。在这些膜中的胍载体的存在下，进一步证实了由未标记的胍的摄取的反式刺激和由丙咪嗪在平衡交换条件下的胍摄取的抑制。（250字处删节）
The characteristics of guanidine uptake were studied in brush-border membrane vesicles isolated from the rabbit proximal intestine. Guanidine uptake was manyfold greater in the presence of an outward-directed H+ gradient (intracellular pH = 5.5; extracellular pH = 7.2) than in the absence of a H+ gradient (intracellular and extracellular pH = 7.2). The time course of guanidine uptake exhibited an overshoot phenomenon in the presence of the H+ gradient, indicating occurrence of uphill transport. This H+ gradient-stimulated guanidine uptake was not due to an inside-negative H+-diffusion potential because carbonyl cyanide 4-trifluoromethoxyphenylhydrazone, a protonophore, failed to have any effect on guanidine uptake. Moreover, the transient uphill transport of guanidine was observed even in voltage-clamped membrane vesicles. However, under the conditions that effectively dissipated the H+ gradient, there was no active transport of guanidine. This H+ gradient-dependent transport mechanism for guanidine is distinct from the Na+-H+ exchanger, because amiloride did not inhibit guanidine uptake even at a concentration as high as 100 microM. These data provide evidence for the presence of a guanidine-H+ antiport system in the rabbit intestinal brush-border membrane. The presence of a carrier for guanidine in these membranes is further substantiated by the trans-stimulation of the uptake of radiolabeled guanidine by unlabeled guanidine and by the inhibition of guanidine uptake by imipramine under equilibrium exchange conditions.(ABSTRACT TRUNCATED AT 250 WORDS)