Digestive Enzyme Adjustments Of Swiss Mouse(Mus Musculus)to Diet Composition

Phenotypic plasticity is an adaptive strategy which forms during a long-term biological evolution process.The phenotypic plasticity of digestive organs morphology and physiology can limit the ratio of animals obtaining energy and nutrition.In the natural environment,animals often experience the changes of food quality and quantity,their digestive organs morphology and the various enzymes activity of intestinal brush border membrane could regulate moderately to meet the demand for energy and nutrient.To explore effect of diet composition on digestion of different ages Swiss mice,We measured daily food intake,internal organs and digestive tract organs morphology,protein concentration of small intestinal tissue and gastric contents of the suckling mice,enzyme activity(disaccharidases and N-aminopeptidase)of intestinal brush border membrane of all mice,and finally analyzed the differences of digestibility and the digestion strategy between different groups.The main results and conclusions were that:1.The postnatal changes of 4 kind digestive enzyme activities of mice intestine were different.The lactase activity increased from birth and then decreased and it reached the highest at 9~12 days of age.There was weak lactase activity at 27 days of age.The sucrase activity which appeared at 12 days of age and increased rapidly from 15 days of age reached the highest at 18~21 days of age and then declined markedly.The maltase activity was weak at birth and maintained at this level before 15 days of age which increased rapidly and reached the peak at 18~21 days of age,and then decreased.Aminopeptidase-N activity of proximal small intestine continued to decline until 27 days of age,while the activity increased continuously from birth to weaning in the middle and distal intestine and then declined slight.The result showed the temporal changes of 4 kinds of enzymes activities in small intestine could match with the variation of food digestion needs.2.Whether different food can affect milk components of lactation mice or not and further affect the development of baby mice.We domesticated lactation mice using high-starch,control and high-protein food on day of parturition.Results showed milk protein concentration of mother mice were impacted significantly by different food,while digestive enzyme activity of small intestinal brush border membrane of young mice were less affected by different food.3.To compare digestion phenotypic plasticity difference between sub-adult and adult mice.We domesticated sub-adult and adult mice in different food for two weeks,and tested and compared feeding digestion,organs morphology,the digestive enzyme activity of small intestine brush border membrane and blood index.The results showed that phenotypic plasticity of small intestinal disaccharidases activity of adult mice was stronger than sub-adult mice's,however the phenotypic plasticity of aminopeptidase-N activity of sub-adult mice was stronger.4.We domesticated lactation mice in high-starch,control and high-protein food.The results showed food intake of lactation mice increased with time continuously,while their digestion rate did not change significantly.The disaccharidases activity of small intestinal brush border membrane of lactation mice supported adaptive modulation hypothesis,but the aminopeptidase-N activity did not support adaptive modulation hypothesis.Serum glucose,triglyceride concentration of lactation mice were no significant difference between different groups,while the concentration of urea nitrogen and creatinine of high starch food group was below the high protein food group significantly.