Effects Of Insulin, IGF-I And Hydrolysed Bovine Colostrum On The Proliferation And Functional Maturation Of Calf Intestinal Epithelial Cells In Vitro

The calf intestinal epithelial cells in vitro (CIEC) were selected to evaluate the trophic actions of insulin, IGF-J and peptic and tryptic hydrolysates of bovine colostrum. The cell proliferation, glucose absorption and specific activity of cell membrane enzymes were investigated. Results showed that insulin with a dosage of 10 ii glint and JGF-I with 1 OOng/ml both had strong stimulating effects on the proliferation and glucose absorption of CIEC (P<0.0 1), while insulin with a dosage of 50 11 g/ml inhibited the proliferation and glucose absorption of CIEC (P<0.0 1). IGF-J with concentration exceeded 1 O0nglml (SOOng/ml and 1 000ng/ml in this experiment) showed saturated effect. This suggested that IGF-J at a dosage of 1 OOng/ml, SOOng/ml or 1 000ng/ml had similar actions. The hydrolysates of bovine colostrum hydrolyzed by pepsin for 90 mm significantly stimulated the proliferation of CIEC (P<0.0 1). The tryptic hydrolysates of bovine colostrum, however, did not display proliferation-stimulating effect at any time. Prolonged treatment of bovine colostrum by pepsin and trypsin strengthened the glucose absorption. This absorption-stimulating effect of hydrolysates reached their maximum at 90 mm of hydrolyzation by trypsin and 150 mm by pepsin (P<0.01). Moreover, the specific activity of alkaline phosphatase (AKP) in the membrane of CIEC was enhanced by peptic and tryptic hydrolysates (P<0.0 1). The Na-K-ATPase was more active as compared with control group when treated by hydrolysates derived from pepsin hydrolyzed bovine colostrum for 90 mm or trypsin hydrolyzed bovine colostrum for 150 mm. Both peptic hydrolysis and tryptic hydrolysis, however, decreased the effect of bovine colostrum on promoting the activity of lactase in the membrane of dEC (P<0.0 1). To inactivate the hydrolase (Pepsin and trypsin), the hydrolysates were incubated at 70 or 100 C, and the effect for this two methods was similar. Additionally, the results showed that the mixed hydrolysates derived from colostrum hydrolyzed by pepsin for 90 mm, together with 1 OOngIml IGF-I, had the most significant stimulating effect on the cell proliferation (P<0.0 1). Tryptic hydrolysates of bovine colostrum for 90 mm containing 10 L~ g/ml Insulin or I OOng/ml IGF-I had the same effect on glucose absorption by CIEC in vitro. The results suggested that natural growth factors in colostrum had significant effect on the proliferation, growth and development of intestinal epithelial cells in vitro. Some bioactive peptides could be extracted from milk protein by suitable enzyme hydrolysis, and the hydrolysates have the function of stimulating the growth and development of intestinal epithelial cells. The biological implications and molecular biochemical mechanism behind the effect need further investigated.