Pantoflickova D, Scott D R, Sachs G, Dorta G, Blum A L
Gastroenterology Department, CHUV-BH10, Lausanne, Switzerland.
Gut. 2003 Jul;52(7):933-7. doi: 10.1136/gut.52.7.933.
Acid test meals may improve the accuracy of the (13)C urea breath test (UBT). This has been attributed to changes in gastric emptying rather than to the effects of gastric pH on Helicobacter pylori urease.
To determine whether enhancement of (13)CO(2) excretion in the UBT in H pylori infected volunteers by acidification of a test meal is due to a delay in gastric emptying.
Urease activity in vitro was measured in intact bacteria and in bacterial homogenates. Urease activity in vivo was assessed by means of the UBT. Eleven H pylori infected subjects underwent UBTs with neutral Ensure (pH 7.0), acidified Ensure (pH 3.0), and apple juice (pH 3.0). Gastric emptying was assessed by (13)C sodium acetate breath test.
From pH 7 to pH 3, the in vitro urease activity of intact bacteria increased sixfold. In contrast, urease activity of bacterial homogenates was inactivated by low pH. In vivo, urease activity, as measured by the UBT 20 minutes after meal ingestion, was higher with apple juice (delta (13)CO(2)=21.1; p=0.03) and acidified Ensure (delta (13)CO(2)=25.5; p=0.01) than with neutral Ensure (delta (13)CO(2)=12.5). Gastric emptying was faster with apple juice (T(max)=36.7 (8) minutes) but not with acidified Ensure (T(max)=63.3 (5) minutes; p=0.06) than with neutral Ensure (T(max)=65.0 (3) minutes; p=0.04).
The higher UBT found with acidified compared with neutral test meals was independent of the emptying rates of the test meals but may have been due to medium acidity dependent activation of intra-bacterial urease in intact H pylori.
胃酸试验餐可提高¹³C尿素呼气试验（UBT）的准确性。这归因于胃排空的变化，而非胃pH值对幽门螺杆菌尿素酶的影响。
确定通过酸化试验餐增强幽门螺杆菌感染志愿者UBT中¹³CO₂排泄是否是由于胃排空延迟。
在完整细菌和细菌匀浆中测量体外尿素酶活性。通过UBT评估体内尿素酶活性。11名幽门螺杆菌感染受试者分别用中性安素（pH 7.0）、酸化安素（pH 3.0）和苹果汁（pH 3.0）进行UBT。通过¹³C醋酸钠呼气试验评估胃排空。
从pH 7降至pH 3，完整细菌的体外尿素酶活性增加了六倍。相比之下，细菌匀浆的尿素酶活性在低pH值下失活。在体内，用餐后20分钟通过UBT测量的尿素酶活性，苹果汁组（δ¹³CO₂ = 21.1；p = 0.03）和酸化安素组（δ¹³CO₂ = 25.5；p = 0.01）高于中性安素组（δ¹³CO₂ = 12.5）。苹果汁组的胃排空更快（Tmax = 36.7 [8]分钟），但酸化安素组（Tmax = 63.3 [5]分钟；p = 0.06）与中性安素组（Tmax = 65.0 [3]分钟；p = 0.04）相比胃排空并不更快。
与中性试验餐相比，酸化试验餐时较高的UBT结果与试验餐的排空速率无关，但可能是由于完整幽门螺杆菌中细菌内尿素酶的中度酸度依赖性激活。
