Vernay M
Br J Nutr. 1987 May;57(3):371-81. doi: 10.1079/bjn19870045.
Interrelations between bacterial metabolites (volatile fatty acids, lactate) in the gut contents and the blood in relation to the faecal excretory cycle (soft or hard faeces) were studied in anaesthetized rabbits. It appeared that the level of organic acids in the alimentary tract varied cyclicly with the faecal excretion pattern. The lactate entering the portal circulation originates from the stomach, while the volatile fatty acids (VFA) originate from the hind-gut. Net absorption from the digestive tract and hepatic utilization of fermentation acids were greater when the rabbits produced hard faeces (hard-phase) compared with soft faeces (soft-phase). Propionate and butyrate reaching the liver were almost quantitatively removed; acetate and lactate were available for extra-hepatic tissue metabolism. Whatever the excretion pattern the levels of VFA in the arterial circulation remained remarkably constant; blood lactate, however, was lower during the soft-phase. Absorption of bacterial metabolites, like their metabolism in the liver, showed a circadian rhythm parallel to the changes in the activity of the adrenal glands, i.e. the activity was enhanced during the hard-phase.
在麻醉的兔子身上研究了肠道内容物中的细菌代谢产物（挥发性脂肪酸、乳酸）与血液之间的相互关系，以及与粪便排泄周期（软便或硬便）的关系。结果表明，消化道中有机酸的水平随粪便排泄模式呈周期性变化。进入门静脉循环的乳酸起源于胃，而挥发性脂肪酸（VFA）起源于后肠。与软便（软便期）相比，兔子产生硬便（硬便期）时，消化道的净吸收和发酵酸的肝脏利用更大。到达肝脏的丙酸和丁酸几乎被定量清除；乙酸和乳酸可用于肝外组织代谢。无论排泄模式如何，动脉循环中VFA的水平都保持显著恒定；然而，软便期的血液乳酸水平较低。细菌代谢产物的吸收，就像它们在肝脏中的代谢一样，呈现出与肾上腺活动变化平行的昼夜节律，即硬便期活动增强。
