锌缺乏对生长期大鼠小肠黏膜形态和消化酶活性的影响

Effect of zinc deficiency on intestinal mucosal morphology and digestive enzyme activity in growing rat

目的了解锌缺乏对大鼠小肠黏膜形态和消化酶活性的影响。方法3周龄刚断乳sD雄性大鼠30只，随机分成3组，每组10只：正常组自由食用含锌30μg／g正常饲料；缺锌组自由食用含锌0．4μg／g的缺锌饲料（参照AIN-76配方）；配饲组食用正常饲料，但进食量限制为缺锌组大鼠前1天的进食量，各组自由饮用去离子水。每日清晨称大鼠体重并记录前1天的进食量，观察有无厌食、腹泻、皮炎、生长迟缓等缺锌的症状。2周后处死，检测血清锌的浓度；留取空肠黏膜作病理切片和HE染色，测定空肠黏膜绒毛高度和隐窝深度的比例；检测空肠黏膜刷状缘乳糖酶、1谷氨酰转肽酶（GGT）和氨基寡肽酶（APN）的活性。结果实验开始时正常组、缺锌组、配饲组大鼠的平均体重分别为（67．4±5．3）g、（64．7±4．8）g和（66．5±4．1）g，平均13进食量分别为（11．2±1．0）g、（11．6±1．6）g和（11．2±1．4）g，差异均无统计学意义。实验第7天缺锌组平均进食量与正常组和配饲组差异不明显，而平均体重则明显低于正常组和配饲组（P〈0．01）；而2周实验结束时缺锌组平均体重为（112．0±11．5）g，明显低于正常组和配饲组的（164．0±15．9）g、（137．5±16．2）g；缺锌组平均进食量（13．4±5．1）g明显低于正常组的（18．2±2．4）g，差异有统计学意义（P均〈0．01）。缺锌组血清锌的含量（733±231）μg／L明显低于正常组的（1553±159）μg/L和配饲组的（1457±216）μg/L（P〈0．01）。三组大鼠空肠黏膜绒毛高度与隐窝深度比例分别为（2．98±0．5）、（2．77±0．5）和（2．81±0．7）；乳糖酶活性分别为（26．1±15．0）U／mg、（27．44-12．8）U／mg和（40．84±18．5）U／mg，差异均无统计学意义。缺锌组空肠黏膜GGT为（12．7±6．5）U／g明显低于正常组的（19．1±10．4）U／g和配饲组的（18．5±7．7）U／g，但差异无统计学意义；缺锌组空肠黏膜APN（25．5±7．5）U／g明显低于正常组的（48．7±16．8）U／g和配饲组的（43．9±14．5）U／g，差异有统计学意义（P〈0．01）。结论锌缺乏可致食欲下降、体重减轻，可引起空肠黏膜刷状缘肽酶活性下降，但对绒毛高度与隐窝深度的比例和乳糖酶活性影响不大，表明锌缺乏最先影响的可能是蛋白质的消化与吸收功能。

Objective In this study, a growing rat model of zinc deficiency was established to investigate the effect of zinc deficiency on intestinal mucosal morphology and digestive enzyme activity as well as to provide a scientific basis for zinc supplementation therapy in patients with diarrhea. Method Three- week-old weaned Sprague-Dawley male rats （n = 30） were randomly divided into 3 groups with 10 in each： rats in the control group （ZA） were fed with a normal diet containing 30 μg/g zinc ; rats in the zinc deficient group （ZD） were fed with a zinc-deficient diet containing 0. 4 μg/g zinc （refer to AIN-76 formula）; and rats in the paired fed group （PF） were fed with a normal diet, but the food intake was limited to intake of rats in ZD group in the previous day. All rats were provided with deionized water for drinking. Their bodyweight was measured and the food intake during the previous day was recorded early in the morning of the following day. Symptoms of zinc deficiency, such as anorexia, diarrhea, dermatitis, and growth retardation, were observed. Two weeks later, the rats were sacrificed and serum zinc concentration was measured. Jejunal mucosa was taken for biopsy and was stained with hematoxylin and eosin （HE）. The height ratio of the jejunal mucosal villi and crypts was measured. In addition, the activity of laetase in the jejunal mucosal brush border, γ-glutamyl peptidase （GGT）, and aminopeptidase N （APN） were measured. Result The average weight of the rats in the ZA, ZD, and PF groups at the beginning of the experiment was （67.4±5.3） g, （64. 7±4. 8 ） g, and （66. 5±4. 1 ） g, respectively, and the average daily food intake was （ 11.2±1.0） g, （ 11.6±1.6） g, and （ 11.2±1.4） g, respectively. The intergroup differences were not significant. On the 7＇h day of experiment, no significant differences in average food intake were observed between the ZD group and the ZA and PF groups, but the average body weight in the ZD group was significantly lower than that in the ZA and PF groups （P 〈0. 01 ）. At the end of the experiment （2 weeks）, the average weight in the ZD group （ 112. 0±11.5） g was significantly lower than that in the ZA （ 164. 0±15.9） gandPFgroups （137.5±16. 2） g. The average food intake in theZDgroup （13.4±5.1） g was significantly lower than that in the ZA group （18. 2±2.4） g （P 〈0. 01 ）. Serum zinc level in the ZD group （733±231 ） μg/L was significantly lower than that in the ZA （1553±159） tzg/L and PF groups （ 1457±216） /xg/L（P 〈0. 01 ）. The height ratio of jejunal mucosa villus and crypt in the ZA, ZD, and PF groups was 2. 98±0. 5, 2. 77±0. 5, and 2. 81± 0. 7, respectively, and laetase activity was （26. 1 ±15.0） U/mg, （ 27.4±12. 8 ） U/mg, and （ 40. 8±18.5 ） U/rag, respectively, without significant intergroup differences. The GGT activity in the jejunal mueosa in the ZD group （ 12. 7±6. 5 ） U/g was significantly lower than that in the ZA （ 19. 1±10. 4 ） U/g and PF groups （ 18.5±7.7 ） U/g, but the difference was not significant. The activity of APN in the jejunal mucosa in the ZD group （25.5±7.5） U/g was significantly lower than that in the ZA （48.7 -＋ 16. 8） U/g and PF groups （43.9 -＋ 14. 5） U/g （P 〈 0. 01 ）. Conclusion Zinc deficiency can eause loss of appetite, weight loss, and decreased activity of peptidase in the jejunal mueosal brush border. Zinc deficiency has little effect on the height ratio of the villus and crypt and lactase activity, thereby indicating that zinc deficiency may first affect protein digestion and absorntion.