Isolation Of Insulin-like Growth Factor-Ⅰ From Bovine Colostrums And Its Hypoglycemic Research

The subject of this research is to separate insulin-like growth factor-Ⅰ(IGF-Ⅰ) from bovine colostrums and to observe its hypoglycemic effect in streptozotocin-induced diabetic rats.The results are as follow: Concentrations of free and bound IGF-Ⅰwere measured in bovine colostrums from the first milkings to 14 day postpartum.Rapid decrease was found during this period. IGF-Ⅰappeared mainly in the free form at 1-5 day colostrums and the ratio varied from 71.1% to 50.64%.After that,bound form dominated and the ratio varied from 51.41% to 60.1%. Using the extraction of acid-ethanol and gel filtration chromatography methods, IGF-Ⅰwas isolated and purified from colostrums.The recovery of IGF-Ⅰwas 97.2% and 58.84%respectively in two process.The content of IGF-Ⅰwas 2.137mg/g,440 times higher than colostrums. The hypoglycemic effect of IGF-Ⅰon streptozotocin-induced diabetic rats was evaluated. The results were: ⑴the bovine colostrum IGF-Ⅰhad obvious hypoglycemic effect in diabetic rats;⑵compared with basic value,plasma glucose value was decreased about 18.21%,14.96% and 14.55% in high,middle and low dose group by oral administration;⑶the glucose value of intraperitoneal group was about 43.23%,better than oral administration;⑷its hypoglycemic effect had persistence and stability. Serum homone level of all rats were measured by radioimmunoassay. The results showed: IGF-Ⅰcould increase serum insulin and free IGF-Ⅰlevel significantly and decrease growth homone level. The curve of glucose resistence descended obviously in administration group.It implied that IGF-Ⅰcould improve glucose resistence of diabetic rats to some degree. The cell of liver and pancreas were observed by micrography.It showed that IGF-Ⅰcould accelerate the glycogenesis and promote the regeneration of residualβ-cell . Based on research results,the hypoglycemic mechanism of IGF-Ⅰwas deduced.It is that ⑴By accelerating the glycogenesis ,IGF-Ⅰcan make good use of serum glucose.In this way,glucose utilization is increased.⑵IGF-Ⅰcan also have the residualβ-cell regenerated so that much more insulin is produced to exert hypoglycemic action.