Halliday C E, Clark C, Farthing M J
Department of Gastroenterology, St Bartholomew's Hospital, West Smithfield, London.
Trans R Soc Trop Med Hyg. 1988;82(3):428-32. doi: 10.1016/0035-9203(88)90153-8.
Giardia lamblia predominantly colonizes the proximal small intestine where bile is plentiful. We have investigated interactions between bile and this parasite by (i) examining the specificity of the stimulatory effect of bile on parasite growth in vitro, (ii) studying the possible association between giardiasis and bile salt deconjugation in vivo, and (iii) quantifying bile salt uptake by Giardia and relating this to uptake by other microorganisms. Our findings indicate that the growth promoting effects of ox bile and pure bile salt (sodium glycocholate) are, as far as is known, specific for Giardia, since the growth of a related protozoon, Trichomonas vaginalis, and a variety of enteric bacteria was either unchanged or inhibited. We were unable to detect deconjugated ('free') bile salt in duodenal fluid from UK patients with giardiasis and found no evidence to suggest that Giardia deconjugated bile salts in vitro. However, Giardia avidly took up conjugated bile salt, apparently in a concentration-dependent manner and to a much greater degree than Trichomonas and enteric bacteria. Thus, bile specifically stimulates growth of Giardia, and bile salt is avidly consumed by the parasite. The mechanism by which bile stimulates parasite growth is unknown, but uptake of conjugated bile salt by Giardia could reduce intraluminal bile salt concentrations and possibly interfere with micellar solubilization of fat. This may contribute to the steatorrhoea which is well recognized in symptomatic patients with giardiasis.
蓝氏贾第鞭毛虫主要寄生于胆汁丰富的近端小肠。我们通过以下方式研究了胆汁与这种寄生虫之间的相互作用：（i）检测胆汁对寄生虫体外生长刺激作用的特异性；（ii）研究贾第虫病与体内胆盐去结合作用之间可能的关联；（iii）量化贾第虫对胆盐的摄取，并将其与其他微生物的摄取情况进行比较。我们的研究结果表明，据目前所知，牛胆汁和纯胆盐（甘氨胆酸钠）的促生长作用对贾第虫具有特异性，因为相关原生动物阴道毛滴虫和多种肠道细菌的生长要么未发生变化，要么受到抑制。我们在英国贾第虫病患者的十二指肠液中未能检测到去结合的（“游离的”）胆盐，并且没有发现证据表明贾第虫在体外会使胆盐去结合。然而，贾第虫能大量摄取结合型胆盐，显然是以浓度依赖的方式，且摄取程度远高于阴道毛滴虫和肠道细菌。因此，胆汁特异性地刺激贾第虫生长，且寄生虫会大量消耗胆盐。胆汁刺激寄生虫生长的机制尚不清楚，但贾第虫摄取结合型胆盐可能会降低肠腔内胆盐浓度，并可能干扰脂肪的胶束增溶作用。这可能导致了贾第虫病有症状患者中常见的脂肪泻。
