Kishore P, Shukla O P
Division of Biochemistry, Central Drug Research Institute, Lucknow, India.
Indian J Exp Biol. 1991 Dec;29(12):1134-9.
The multiplication of A. culbertsoni in the peptone medium was not inhibited by 10-20 mM concentration of alpha-difluoromethyl ornithine (DMFO) while a partial and transient inhibition of cell multiplication was observed by 10-20 mM DFMO in proteose peptone, yeast extract, glucose (PYG) medium. Ornithine decarboxylase (ODC) activity in the cells and cell free extracts was strongly inhibited by DFMO, excluding enzyme refractoriness and impermeability of cells for DFMO as the possible causes of DFMO resistance. The presence of polyamines in the peptone and PYG media as well as uptake of polyamines by the amoebae has been demonstrated. The growth and multiplication of A. culbertsoni in chemically defined medium was not affected by 1-5 mM DFMO while 10-20 mM DMFO yielded partial inhibition. A lowering of diaminopropane levels and enhancement of spermidine levels was observed in DFMO inhibited cells and level of ODC was drastically reduced in the inhibited cultures. Uptake of polyamines from the growth media may partly account for DFMO resistance of A. culbertsoni. Alternative mechanisms for DFMO resistance are indicated.
在蛋白胨培养基中，10 - 20 mM浓度的α-二氟甲基鸟氨酸（DMFO）不会抑制库尔伯特变形虫（A. culbertsoni）的增殖，而在蛋白胨、酵母提取物、葡萄糖（PYG）培养基中，10 - 20 mM的DFMO会观察到细胞增殖受到部分且短暂的抑制。细胞及无细胞提取物中的鸟氨酸脱羧酶（ODC）活性受到DFMO的强烈抑制，排除了酶难治性和细胞对DFMO不渗透性作为DFMO抗性可能原因的可能性。已证明蛋白胨和PYG培养基中存在多胺以及变形虫对多胺的摄取。在化学成分确定的培养基中，1 - 5 mM的DFMO不会影响库尔伯特变形虫的生长和增殖，而10 - 20 mM的DMFO会产生部分抑制作用。在DFMO抑制的细胞中观察到二氨基丙烷水平降低和亚精胺水平升高，并且ODC水平在受抑制的培养物中急剧降低。从生长培养基中摄取多胺可能部分解释了库尔伯特变形虫对DFMO的抗性。还指出了DFMO抗性的其他机制。
