The effect of growth hormone-releasing peptide-2 (KP102) administration on plasma insulin-like growth factor (IGF)-1 and IGF-binding proteins in Holstein steers on different planes of nutrition.
This study was conducted to investigate the nutrition-dependent changes in insulin-like growth factor (IGF)-1 and IGF-binding proteins (IGFBPs) with growth hormone releasing peptide-2 (D-Ala-D-betaNal-Ala-Trp-D-Phe-Lys-NH(2); GHRP-2 or KP102) treatment in growing Holstein steers. Eight 13 month-old Holstein steers were grouped on two levels of feed intake (high intake (HI); 2.43% body weight or low intake (LI); 1.22%) and each group was daily injected with KP102 (12.5 microg/kg body weight/day) or saline solution into the jugular vein during 6-day period. The concentration of plasma GH showed an increase after an i.v. bolus injection of KP102 on Day 1 and Day 6 in both the LI and HI groups. Plasma IGF-1 began to increase 10 hr following an i.v. bolus injection of KP102, but this was only observed in the HI group (P < 0.05). Also, the plasma IGF-1 in the HI group with daily injections was significantly greater than the LI group from Day 1 of KP102 administration (P < 0.05). It reached maximum values of 125.1 +/- 7.6 ng/ml after Day 2, and returned to pre-injection levels after Day 4, however, no change in plasma IGF-1 was observed in LI with administration of KP102. During 6 days of treatment, plasma 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 were significantly higher in KP102 treated steers but only in the HI group (P < 0.05). Plasma 34 kDa IGFBP-2 decreased in the HI group and did not show any change following an injection of KP102. In conclusion, the effect of stimulated endogenous GH with KP102 administration increased plasma IGF-1, 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 levels in the HI group of growing Holstein steers, but not in the LI one. Thus, we strongly believe that the plasma IGF-1 and IGFBPs response to KP102 treatment is modulated by the nutritional status of growing Holstein steers and the increased plasma IGF-1 concentration with KP102 treatment may be regulated by plasma 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 in Holstein steers.
Lee
H G
HG
Laboratory of Animal Production, Department of Animal Science, Obihiro University of Agriculture and Veterinary Medicine Inada-cho, Obihiro, Japan.
Vega
R A
RA
Phung
L T
LT
Matsunaga
N
N
Kuwayama
H
H
Hidari
H
H
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D019540:Area Under Curve; D001806:Blood Urea Nitrogen; D015153:Blotting, Western / Q000662:veterinary; D002417:Cattle / Q000502:physiology*; D004435:Eating / Q000502:physiology; D013006:Growth Hormone / Q000097:blood / Q000502:physiology*; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology; D006728:Hormones / Q000008:administration & dosage / Q000494:pharmacology; D007328:Insulin / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D016014:Linear Models; D008297:Male; D009584:Nitrogen / Q000032:analysis; D009752:Nutritional Status; D009842:Oligopeptides / Q000008:administration & dosage / Q000494:pharmacology*; D011863:Radioimmunoassay / Q000662:veterinary
D006728:Hormones; D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins; D009842:Oligopeptides; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; C091874:growth hormone-releasing peptide-2; D009584:Nitrogen