Long-term somatotropic and galactopoietic effects of a (1-30) ethyl amide analog of growth hormone-releasing factor.
Thirty-five lactating Holstein cows (165 +/- 8 DIM) received the following treatments for 96 d: uninfused controls; i.v. infusion of .9, 2.7, or 8.1 mg/d of Ile2, Ser8.28, Ala15, Leu27, Hse30-bovine growth hormone-releasing factor (1-30) ethyl amide; or i.v. infusion of 12 mg/d of recombinant Leu27, Hse45-bovine growth hormone-releasing factor (1-45) lactone. Concentrations of somatotropin in serum and SCM yield of cows infused with 1-30 releasing factor increased quadratically as the dose increased. Responses for somatotropin and SCM yield were quantitatively similar for cows infused with 2.7 and 8.1 mg of 1-30 or 12 mg of 1-45. While concurrently infused with the 1-30 or 1-45 as described, cows retained their ability to release somatotropin following an acute i.v. injection of 10 nmol/100 kg of BW of either growth hormone-releasing factor 1-30 or 1-45. Mean concentrations of IGF-I in serum increased similarly in magnitude for cows infused at all doses of 1-30 or 1-45. The 1-30 releasing factor generally increased IGF-binding protein-3, but had little effect on IGF-binding protein-2. The 1-45 releasing factor did not significantly affect either binding protein. Yield of SCM was correlated with serum concentrations of somatotropin, but not with IGF-I. Concentrations of NEFA in serum were elevated through 36 and 50 d in response to the highest doses of 1-30 and 1-45, respectively. Treatment did not affect DMI, BW, or body condition score.(ABSTRACT TRUNCATED AT 250 WORDS)
Tucker
H A
HA
Department of Animal Science, Michigan State University, East Lansing 48824, USA.
Terhune
A L
AL
Chapin
L T
LT
VandeHaar
M J
MJ
Sharma
B K
BK
Moseley
W M
WM
D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007700:Kinetics; D007774:Lactation / Q000187:drug effects*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology*; D011897:Random Allocation; D011994:Recombinant Proteins / Q000494:pharmacology
D005230:Fatty Acids, Nonesterified; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D010446:Peptide Fragments; D011994:Recombinant Proteins; C096458:U 90349E; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone