呼気中水素測定法および輸送電位測定法による小腸糖消化吸収能の検討

Assessment of Intestinal Absorptive Capacity for Sugar by Measurement of Breath Hydrogen and Transmural Potential Difference

要旨　呼気中水素測定法および輸送電位測定法により糖質の消化吸収能について検討した．われわれが作製した閉鎖循環式回路（closed system）を用いた呼気中水素測定法によるキシロース試験では，全水素排出量を測定時間（180分）で除して得られる平均呼気中水素排出量と5時間尿中キシロース排泄量との間に有意の相関が認められ，短腸症候群症例のみが平均呼気中水素排出量0.19ml/min以上の高値を示した．本法は従来の尿中排泄量測定法に比し腎機能に影響されず老年者を含めた吸収不良症候群の吸収試験法として有用である．open systemによる呼気中水素測定法を用いてデキストリン大量投与時の消化吸収能と加齢との関連を検討した結果では，70歳未満の健常者では200g負荷時にも呼気中水素濃度の上昇はみられなかったのに対し，70歳以上の老年者では有意の高頻度で呼気中水素濃度の上昇がみられた．これは，加齢と小腸通過時間には関連が認められないことからデキストリンの小腸での消化吸収が不十分であることが主因と考えられ，70歳を超える老年者では糖質に対する忍容力の低下することが示唆された．糖輸送電位測定法による肝疾患における糖質の消化吸収能についての検討では，D-glucoseは肝疾患，特に肝硬変でも吸収障害は認められなかったが，二糖類のsucrose，maltoseについては肝硬変でPD_max，K_tの低下傾向が認められた．刷子縁のdisaccharidase活性低下に起因する可能性が考えられる．

　Firstly, breath hydrogen wasmeasured to delineate the absorptive capacity for sugars by our closed circulation system. There was a good correlation between the mean increase in breath hydrogen and D-xylose in urine five hour after loading of 25 g D-xylose. A mean increase of more than 1.9 ml/min in breath hydrogen was observed only in patients with short bowel syndrome. As an absorption test the hydrogen measurement after D-xylose loading may be more useful than the conventional D-xylose test since the breath test can be performed even for patients with malabsorption syndrome regardless of their age or renal function.

　By the H₂ breath test unit (open system) the increased breath hydrogen after loading of 200 g dextrin was observed more frequently in aged subjects over the age of 70 than in any other age (p＜0.01). Small intestinal transit time in aged subjects was not different from that in younger subjects, suggesting an impairment of absorptive capacity for sugar in the aged.

　Secondly, the absorptive capacity for sugar in patients with liver diseases was revealed by measurement of the transmural potential difference across the small intestine. Although D-glucose was absorbed normally in patients with liver diseases, the PD_max and K_t for the active electrogenic component of sucrose and maltose absorption in patients with liver cirrhosis seemed to be lower than those in the control group. This decrease may be derived from decreased activity of disaccharidases in the brush border in patients with liver cirrhosis.