Increased secretion of insulin-like growth factor I into milk of cows treated with recombinantly derived bovine growth hormone.
Six lactating, non-pregnant Jersey cows were given subcutaneous injections of recombinantly derived bovine growth hormone for 7 d. Milk yield was increased by 4.5 kg/d on d 7, compared with the average yield of 10.7 +/- 0.4 kg/d (mean +/- s.e.m.) for the 7 d preceding treatment. Concentrations of insulin-like growth factor I (IGF-I) in the milk increased from 0.44 +/- 0.04 nmol/l (mean +/- s.e.m.) during the 7 d preceding treatment to 1.6 +/- 0.2 nmol/l on d 7 of treatment. Taking the increase in milk yield into account the total increase in the secretion of IGF-I into milk of one udder half was 6-fold. Plasma concentrations of total IGF-I rose from 15.5 +/- 1.3 nmol/l (mean +/- s.e.m.) on the day preceding treatment to 56.9 +/- 3.6 nmol/l (mean +/- s.e.m.) on d 7 of treatment. Mammary plasma flow increased from 1.6 +/- 0.09 to 2.2 +/- 0.06 l/min.udder half over the same time. Estimates of the amount of IGF-I that reached the mammary gland gave values of 24 and 116 nmol/min.udder half before and during treatment respectively. IGF-I in milk of treated cows was associated predominantly with proteins ranging from 40,000 to 150,000 mol.wt, but a significant proportion (19%) of the total IGF-I was present in the free unbound form. IGF-I crosslinking studies revealed the presence in milk of one specifically labelled band at 31,000 mol.wt.
Prosser
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CG
AFRC Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, UK.
Fleet
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IR
Corps
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D000818:Animals; D002417:Cattle / Q000502:physiology*; D005260:Female; D013006:Growth Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007279:Injections, Subcutaneous; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000097:blood / Q000378:metabolism*; D007774:Lactation / Q000097:blood / Q000187:drug effects*; D008892:Milk / Q000032:analysis*; D011247:Pregnancy; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D013002:Somatomedins / Q000378:metabolism*
D011994:Recombinant Proteins; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone