Destripeptide insulin-like growth factor-I in milk from bovine somatotropin-treated cows.
Total somatomedins from milk of bovine somatotropin-treated cows were isolated and characterized to determine the relative amount of the three amino acid N-terminally truncated form of IGF-I (destripeptide IGF-I). The somatomedin fraction was isolated using organic solvent and solid-phase extractions followed by preparative reverse phase HPLC and affinity chromatography. The overall yield of IGF-I was 28%, and destripeptide IGF-I was recovered with similar efficiency. The isolated somatomedins were resolved by capillary zonal electrophoresis and identified using recombinant somatomedin standards. The concentration of destripeptide IGF-I relative to full length IGF-I was determined by amino terminal sequencing and by bioassay. Results from these experiments indicated that the level of destripeptide IGF-I in milk from somatotropin-treated cows was less than 3% of the IGF-I concentration. Destripeptide IGF-I is therefore a minor component of the somatomedins present in milk from treated cows and does not contribute significantly to the proliferative activity of this milk.
Shimamoto
G T
GT
Animal Sciences Division, Monsanto Company, St. Louis, Missouri 63198.
Byatt
J C
JC
Jennings
M G
MG
Comens-Keller
P G
PG
Collier
R J
RJ
D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D013006:Growth Hormone / Q000494:pharmacology*; D008892:Milk / Q000737:chemistry* / Q000187:drug effects; D011863:Radioimmunoassay; D013002:Somatomedins / Q000032:analysis*
D013002:Somatomedins; D013006:Growth Hormone