We determined the activities of lactase, sucrase, maltase and aminopeptidase-N in small intestine of mice from birth to 27 days of age in order to identify the formation and development model of intestinal digestive enzyme activities in young mice and test the adaptive modulation hypothesis. The lactase specific-mass activity increased initially and then decreased, reachingthe highest levels at 9 days of age in the proximal small intestine and at 12 days of age in the middle and distal small intestine. At 27 days of age, there was weak lactase activity only in the middle small intestine. The sucrase specific-mass activity appeared at 12 days of age, and increased rapidly from 15 days of age, reaching the highest level at 18 days of age in the proximal and distal intestine and at 21 days of age in the middle small intestine, and then declined markedly. The maltase specific-mass activity is weak at birth and remained at this level until 15 days of age. It then increased rapidly and reached the peak at 18 days of age in the proximal and distal intestine and at 21 days of age in the middle intestine, and then decreased. The aminopeptidase-N specific-mass activity of proximal small intestine decline continuously until 27 days of age, but the activity increased continuously from birth to weaning in the middle and distal intestine and then slightly declined. The total lactase activity peaked at 15 days of age and then declined. However, the total activities of sucrase, maltase, and aminopeptidase-N constantly increased through the entire lactation period. All

four enzyme specific-mass activities had remarkable differences among the varied positions of the small intestine. Moreover, the age of mice had significant influence on the distribution of enzyme activity in the different small intestine positions. In sum, the temporal changes of the four kinds of enzymes activities in small intestine could match with the variation of food digestion needs, which partly supported the adaptive modulation hypothesis.

为明确晚成型小鼠胎后发育肠道消化酶活力的建立过程和发育模式，探讨其与适应性调节假说的关系，测定了从出生后至27日龄小鼠小肠前、中、后段的乳糖酶、蔗糖酶、麦芽糖酶和氨基肽酶的酶活力。结果发现单位组织酶活力方面，乳糖酶活力先增后降，小肠前段在9日龄而中后段在12日龄达到最高，至27日龄时仅中段有微弱的酶活力；蔗糖酶活力12日龄始出现，前段和后段自15日龄迅速升高，至18日龄达最高，但随后显著降低，而中段在15日龄后持续升高至21日龄达到最高，此后维持在较高水平；麦芽糖酶出生时已具有活力，但在15日龄前维持较低水平，此后迅速升高，前后段在18日龄，中段在21日龄达到峰值，此后下降；小肠前段的氨基肽酶活力出生后至27日龄持续下降，而后段和中段从出生到断乳前则持续升高，断乳后略有下降。除乳糖酶总酶活力先增后降，在15日龄达峰值外，其余3种酶的总酶活力均持续增加。在小肠不同位置4种酶活力的分布具有显著差异，且日龄对不同位置酶活力的影响趋势不同。总之，小鼠小肠4种消化酶的酶活力随时间的变化能够与其食物转变的消化需求相匹配，部分地支持适应性调节假说。