Kobayashi M, Iseki K, Sugawara M, Miyazaki K
Department of Pharmacy, Hokkaido University Hospital, School of Medicine, Sapporo, Japan.
Biochim Biophys Acta. 1993 Sep 19;1151(2):161-7. doi: 10.1016/0005-2736(93)90100-e.
Na(+)-independent uptake rate and binding to the membrane surface of polyamines (spermine, spermidine and putrescine) have been characterized using rat small intestinal brush-border membrane vesicles. The uptake of spermine and spermidine was saturable (Km = 30.4 microM and 148.1 microM, respectively), however, putrescine uptake was not saturable up to 8 mM. In contrast, the values of binding to the membrane surface of all polyamines were not saturable in the present studies. In Dixon plot analysis, spermine competitively inhibited the uptake rate of spermidine with a Ki value of 33.8 microM, while the putrescine inhibitory effect on the spermidine uptake rate was non-competitive (Ki = 3.28 mM). These uptake systems were not affected by the valinomycin-induced K(+)-diffusion potential (inside negative). These results suggested that there were two different Na(+)-independent uptake systems for spermine and spermidine, as well as for putrescine, on this membrane. However, they were not the same as the electric potential-dependent uptake system for monocationic compounds. Furthermore, this uptake system for spermine and spermidine might not be a carrier protein, because the intravesicular spermine exhibited no trans-stimulation effect on the uptake of spermidine.
利用大鼠小肠刷状缘膜囊泡对多胺（精胺、亚精胺和腐胺）的钠离子非依赖性摄取速率及其与膜表面的结合进行了表征。精胺和亚精胺的摄取是可饱和的（Km分别为30.4微摩尔和148.1微摩尔），然而，在高达8毫摩尔时腐胺的摄取是不饱和的。相比之下，在本研究中所有多胺与膜表面结合的值均不饱和。在狄克逊图分析中，精胺竞争性抑制亚精胺的摄取速率，Ki值为33.8微摩尔，而腐胺对亚精胺摄取速率的抑制作用是非竞争性的（Ki = 3.28毫摩尔）。这些摄取系统不受缬氨霉素诱导的钾离子扩散电位（内侧为负）的影响。这些结果表明，在该膜上存在两种不同的钠离子非依赖性摄取系统，分别用于精胺和亚精胺以及腐胺。然而，它们与单阳离子化合物的电位依赖性摄取系统不同。此外，这种精胺和亚精胺的摄取系统可能不是载体蛋白，因为囊泡内的精胺对亚精胺的摄取没有表现出反刺激作用。
