Booden T, Albach R A, Boonlayangoor P
Arch Invest Med (Mex). 1978;9 Suppl 1:133-40.
This study was conducted to determine the mode(s) of uptake of selected pyrimidine bases and nucleosides by axenically grown Entamoeba histolytica. Two-minute uptake studies with 3H-labeled compounds showed the following: 1) uridine and cytidine are taken up, in part, by a carrier mediated system; 2) uracil, cytosine, thymine and thymidine enter amebae via passive diffusion; both cytidine and uridine are taken up by passive diffusion when present at exogenous concentration greater than 500 muM; 3) specific carrier sites are used for transport of uridine-cytidine and uridine-adenosine; 4) cytidine and uridine uptake is markedly inhibited by iodoacetate and N-ethylmalemide; 5) hypoxanthine (10mM) stimulates uptake of uridine; 6) ribose fails to inhibit uptake of cytidine and uridine; 7) cytidine uptake exceeds that of uridine (i.e., apparent Vmax for: a) cytidine = 10.0 nmoles/2 min/10(6) amebae; b) uridine = 3.0 nmoles/2 min/10(6) amebae); 8) Kt for: cytidine = 0.30 mM; uridine = 0.21 mM; 9) Q 10's at 35.5 C vs 25.5 C for: a) cytidine = 3.9; b) uridine = 2.6.
本研究旨在确定无菌培养的溶组织内阿米巴对选定嘧啶碱基和核苷的摄取模式。对3H标记化合物进行的两分钟摄取研究结果如下：1）尿苷和胞苷部分通过载体介导系统摄取；2）尿嘧啶、胞嘧啶、胸腺嘧啶和胸腺苷通过被动扩散进入阿米巴；当外源浓度大于500μM时，胞苷和尿苷均通过被动扩散摄取；3）特定载体位点用于尿苷-胞苷和尿苷-腺苷的转运；4）碘乙酸盐和N-乙基马来酰胺显著抑制胞苷和尿苷的摄取；5）次黄嘌呤（10mM）刺激尿苷的摄取；6）核糖不能抑制胞苷和尿苷的摄取；7）胞苷的摄取超过尿苷（即表观Vmax为：a）胞苷=10.0纳摩尔/2分钟/10⁶个阿米巴；b）尿苷=3.0纳摩尔/2分钟/10⁶个阿米巴）；8）胞苷的Kt=0.30mM；尿苷的Kt=0.21mM；9）在35.5℃与25.5℃时的Q₁₀值为：a）胞苷=3.9；b）尿苷=2.6。
