| Glucocorticoid is a main kind of hormone excreted by stressed animals. It can change the absorption of nutrients in animal's intestine. Three experiments below were designed to investigate the effects of glucocorticoid on the glucose absorption of jejunum brush border membrane in broilers and its mechanism:Trial One: Effects of Glucocorticoid on Glucose Absorption of Brush Border Membrane of the Jejunum in BroilersIn order to study how glucose is absorbed in the jejunum of broilers and its mechanism of regulation, this experiment was designed to investigate the effects of different dose of dexamethasone, a kind of glucocorticoid-like drug, on glucose absorption in the jejunum of broilers by brush border membrane vesicles and radioactive isotope. 24 Arbor Acres broilers with similar body weight were randomly assigned to four treaments at 21 days of age, three of them were injected with dexamethasone 5mg, 1mg and 0.1 mg per kilogram body weight (BW) into abdomen subcutaneously for 7 days, respectively, and the control was injected with saline solution. At the end of experiment, the jejunum was removed for the preparation of BBMV, which was incubated in [~3H]-glucose-contained solution for measuring the absorption of glucose in the jejunum of broilers. The results showed as follows: (1) Dexamethasone restrained the body weight gains of broilers significantly (P<0.05), and the effect of restraint depended on the dose of the dexamethasone injected; (2) Compared with control, dexamethasone-treated groups significantly increased the content of plasma glucose (P<0.05); (3) Dexamethasone restrained the the plasma endogenetic corticosterone level of broilers (P<0.05). At the same time, dishevelment of feather and diarrhea were observed in broilers. Those phenomenons are similar with those that happen when birds suffer stress. It indicated that dexamethasone had the similar effects with the glucocorticoid. In addition, dexamethasone restrained the absorption of jejunum BBMV on glucose in broilers significantly (P<0.05), and the effect of restraint depended on the dose of dexamethasone.Trial Two: Effects of Glucocorticoid on Jejunum Mucosa Disacchridase Activities and Morphology in BroilersThis trial was designed to investigate the effect of glucocorticoid on jejunum mucosa disacchridase activities and morphology of broilers. 36 Arbor Acres broilers with similar weight were randomly assigned into four treatments at 21 days of age, three of them were injected with dexamethasone 5mg, 1mg and 0.1mg per kilogram body weight (BW) into abdomen subcutaneously for 7 days, respectively, and the control was injected with saline solution. The results showed as follows: (1) The dexamethasone restrained the growth of broilers significantly, and the effect was depended on the dose of dexamethasone (P<0.05); (2) There were no significant differences found in both sucrase and maltase activities between control and dexamethasone-treated groups (P>0.05). (3) The dexamethasone decreased the villus height, the absorption area and the value of villus height/ crypt depth in broilers' jejunum significantly (P<0.05). The crypt depth of the group injected with dexamethasone 5 mg/kg BW was significantly deeper than that of control (P<0.05). But dexamethasone did not have significant effect on the villus width and lamina propria mucosa thickness in broilers' jejunum(P>0.05). The results suggested that the growth restraint of broilers caused by stress might be related to the secretion of glucocorticoid which gave rise to the decrease of villus height, absorption area and the increase of crypt depth in broilers' intestine, and then impaired the absorption function of broilers' intestine.Trial Three: Effect of Glucocorticoid on the Expression of Glucose Transporters mRNA of the Jejunum in BroilersThis trial was designed to investigate the effect of long-time injection of dexamethasone on the expressions of Na~+-glucose cotransporters (SGLT1) and facilitative transporter (GLUT2) mRNA in the jejunum of broilers. 24 Abro Acres broilers with the similar weight were randomly assigned into four treatments at 21 days of age, three of them were injected with dexamethasone 5mg, 1mg and 0.1mg/kgBW into abdomen subcutaneously for 7 days, respectively. The volume of injection was diluted to 1 ml with saline solution. And the control group was injected with the same volume of saline solution. The result showed the expression level of SGLT1 mRNA of control group was significantly higher than that of dexamethasone-injected groups(P<0.05), but there were no significant differences among dexamethasone-injected groups(P>0.05); And the expression level of GLUT2 mRNA of groups injected with 0.1mg and 1mg/kgBW dexamethasone was significantly higher than that of control group(P<0.05). The expression level of GLUT2 mRNA of group injected with 5 mg/kgBW dexamethasone was just slightly higher than that of control group (P>0.05). Those results indicated that glucocorticoid might regulate the glucose absorption in the jejunum of broilers by changing the expression level of SGLT1 mRNA.According to the results above, we can conclude that glucocorticoid restrained the glucose absorption of jejunum brush border membrane in broilers according the trials above. And glucocorticoid regulated the glucose absorption of jejunum in broilers by changing the instestine muscoa morphology and expression of SGLT1 mRNA.
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