Naim M, Zechman J M, Brand J G, Kare M R, Sandovsky V
Proc Soc Exp Biol Med. 1985 Mar;178(3):392-401. doi: 10.3181/00379727-178-42022.
Rats fed a diet containing 2.5% sodium saccharin (NaSacc) displayed a rapid (24-36 hr) increase in tryptic and chymotryptic activity in the lower half of the small intestine and the cecum compared with control animals. Cecal pH of rats fed NaSacc was lower than controls. The effect of NaSacc on enzymatic activity of intestinal contents and on indigenous bacterial microflora was studied further in vitro. Intestinal contents incubated anaerobically with or without NaSacc revealed that the presence of NaSacc led to higher tryptic and chymotryptic activity and higher final pH. Changes in pH do not appear, however, to be important for the increased proteolytic activity induced by NaSacc since autodigestion of trypsin and chymotrypsin in filter-sterilized samples was only slightly affected by pH during in vitro incubation. Amylolytic activity, on the other hand, was stabilized by higher pH values. Saccharin stabilized chymotryptic and led to almost complete loss of amylolytic activity during incubation of filter-sterilized samples maintained at adjusted pH values. The amount of reducing sugars remaining in the NaSacc-containing contents from either cecum (in vivo) or from in vitro incubation of unsterilized small intestinal samples was greater than controls not containing NaSacc. The growth of six bacterial strains isolated from small intestinal contents and incubated in laboratory media was inhibited by NaSacc. Extracellular proteolytic activity from bacterial sources was undetectable after incubation of intestinal bacteria in laboratory media. The present results suggest that the effect of NaSacc upon digestive enzyme composition in the small intestine of rats is not mediated through a direct physiological effect of NaSacc on pancreatic exocrine secretion. It is hypothesized that an inhibition of enzymatic activity by NaSacc in the small intestine and the bacteriostatic effect of NaSacc on bacteria may be responsible for the increased proteolytic activity observed in vivo in the cecum following the feeding of a NaSacc-containing diet to rats.
与对照动物相比，喂食含2.5%糖精钠（NaSacc）日粮的大鼠在小肠下半部和盲肠中的胰蛋白酶和糜蛋白酶活性迅速（24 - 36小时）增加。喂食NaSacc的大鼠盲肠pH低于对照组。进一步在体外研究了NaSacc对肠内容物酶活性和肠道固有细菌菌群的影响。在有无NaSacc的情况下厌氧培养肠内容物发现，NaSacc的存在导致更高的胰蛋白酶和糜蛋白酶活性以及更高的最终pH。然而，pH的变化似乎对NaSacc诱导的蛋白水解活性增加并不重要，因为在体外培养期间，过滤除菌样品中胰蛋白酶和糜蛋白酶的自消化仅受到pH的轻微影响。另一方面，淀粉分解活性在较高pH值下得到稳定。在保持调整后pH值的过滤除菌样品培养期间，糖精使糜蛋白酶稳定并导致淀粉分解活性几乎完全丧失。来自盲肠（体内）或未灭菌小肠样品体外培养的含NaSacc的肠内容物中剩余的还原糖量大于不含NaSacc的对照组。从肠内容物中分离并在实验室培养基中培养的六种细菌菌株的生长受到NaSacc的抑制。在实验室培养基中培养肠道细菌后，未检测到来自细菌源的细胞外蛋白水解活性。目前的结果表明，NaSacc对大鼠小肠消化酶组成的影响不是通过NaSacc对胰腺外分泌的直接生理作用介导的。据推测，NaSacc对小肠中酶活性的抑制以及NaSacc对细菌的抑菌作用可能是在给大鼠喂食含NaSacc日粮后在体内盲肠中观察到的蛋白水解活性增加的原因。
