Regulation Of Insulin Like Growth Factor I On Rumen Epithelium Growth And Development In Neonatal Ruminant

In this thesis, effect of insulin like growth factor I (IGF-I) on rumen epithelium growth and development was studied in vitro and vivo. And the substitute of IGF-I has been probed. I. Effect of Pentagastrin and IGF-I on the development and renewal of rumen epithelium.1. Pentagastrin at the concentration of 0 (control), 10-11M, 10-10M and 10-9M were administrated to the cell culture of neonatal male calfs and adult dairy cows. It was found that none of the three doses (10-11M, 10-10M and 10-9M) increased the DNA synthesis of rumen epithelial cells (REC) in neonatal male calfs. But in adult dairy cows, 10-10M and 10-9M exhibited an increase of DNA synthesis by 23.28% (P=0.21) and 10.76% (P=0.14), respectively; compared with the control, 10-11M had no significant difference.2. IGF-I at the concentration of 0 (control), 25ng/ml, 100ng/ml and 200ng/ml were administrated to the cell culture of neonatal male calfs. It was found that all of the three doses (25ng/ml, 100ng/ml and 200ng/ml) increased the REC DNA synthesis by 26.52%(P<0.01), 70.10%(P<0.05), and 53.16%(P<0.01), respectively. Using 0(control), 25ng/ml, 50ng/ml, 100ng/ml and 200ng/ml IGF-I in the culture of dairy REC. It was found that 25ng/ml and 50ng/ml exhibited a significant improve of DNA synthesis; the dose of 100ng/ml increased the DNA synthesis, but didn't arrived the significant level. Compared with control, the DNA synthesis of 25ng/ml, 50ng/ml and 100ng/ml were increased by 14.84% (P<0.05) , 13.26% (P<0.05) and 12.73%(P=0.16), respectively; and 200ng/ml exhibited a little fall.These experiments provide the evidences that the effect of Pentagastrin and IGF-I on the development and renewal of REC has age character. Pentagastrin promotes DNA synthesis of REC in adult cow. But it has no significant elevation in neonatal calfs. IGF-I improves DNA synthesis of REC both in neonatal calfs and in adult cows. But the sensitivity of IGF-I in neonatal calfs is highter than that in adult cows.II. Effect of crude rhIGF-I preparation on the growth and development of rumen epithelium in neonatal lambs.Eight native suckled lambs were divided into 2 groups based on their weight. The treated group received crude rhIGF-I (1mg·kg-1·day-1) preparation and the control received distilled water from14d to 24d after birth. Lambs were killed and rumen epithelium was collected. The tissue was used to study [3H] thymidine incorporation in vitro, analyse its DNA, RNA content, and the change of its paillae. It was found that oral administration of crude rhIGF-I preparation increased the DNA content significantly by 31%(P<0.01) compared with the control group. And the RNA content was improved by 14.55%(P=0.217), but not on significant level. The number of paillaes was increased.These results demonstrate that oral administration of crude rhIGF-I preparation froml4d to 24d after birth significantly increased rumen epithelium growth and development in suckled neonatal lambs.III. Effect of oral administrated of cysteamine (CS) on the growth in neonatal lambs.Eight native suckled lambs were divided into 2 groups based on their weight. Thetreated group were oral infused with CS (9mg · kg-1· day-1) and the control with distilledwater from14d to 49d after birth. Result showed that CS increased weight gain by 16.87%(P=0.16). The DNA content of rumen epithelium was increased a little. And no significantchange was found on the RNA content of rumen epithelium.Twin 2-month-old unsuckled lambs (n=6) received CS (9mg· kg-1 · day-1) for 24 days. Result showed that CS increased weight gain by 8.32% (P<0.05) .These results demonstrate that oral administration of CS increased weight gain both in suckled and unsuckled lambs. It seemed that oral CS increased rumen epithelium growth and development in suckled neonatal lambs.