Effect of somatotropin and/or equine chorionic gonadotropin on serum and follicular insulin-like growth factor I and insulin-like growth factor binding proteins in cattle.
We investigated the effect of administration of somatotropin (ST) and/or eCG on insulin-like growth factor I (IGF-I) and IGF-binding proteins (IGFBP) in serum and follicular fluid (FFL) of cattle actively immunized against growth hormone-releasing factor (GRF). Cyclic beef cattle, previously immunized against GRF-(1-29)-Gly-Gly-Cys-NH2 conjugated to human serum albumin (synthesized and provided by Hoffmann-LaRoche, Inc., Nutley, NJ; GRFi, n = 31) or to human serum albumin alone (HSAi, n = 26), received (i.m.): 1) 25 mg recombinantly derived methionyl somatotropin (rbST, n = 14; sometribove provided by Monsanto Co., St. Louis, MO); 2) 1100 IU eCG (n = 10); 3) rbST and eCG (rbST-eCG, n = 15); or 4) vehicle (VEH, n = 17) at 0 and 24 h after receiving prostaglandin F2 alpha (PGF2 alpha). Serum samples were collected at 0 and 40 h after PGF2 alpha, and the ovary bearing the largest follicle (DOM) was removed 44.0 +/- 0.5 h after PGF2 alpha; FFL was harvested from DOM and the subordinate follicle (SUB). Before treatment (0 h), GRFi cows had lower serum ST (0.6 +/- 0.2 vs. 2.2 +/- 0.2 ng/ml; p < 0.01) and IGF-I (26 +/- 4 vs. 72 +/- 4 ng/ml; p < 0.01), but greater IGFBP-2 (594 +/- 48 vs. 384 +/- 52 ng/ml; p < 0.01) than HSAi cows. Serum and FFL concentrations of IGF-I or IGFBP-2 were not different between rbST- and rbST-eCG-treated cows or between VEH- and eCG-treated cows at Hour 40 after the initial treatment injection; therefore, data were combined and designated as rbST and VEH, respectively. Serum IGF-I was increased to a greater extent (percentage increase above 0 h) by rbST treatment in GRFi (362 +/- 24) than in HSAi (176 +/- 16) cows (immunization by treatment, p < 0.01). Across GRFi and HSAi, rbST lowered serum IGFBP-2 (342 +/- 31 vs. 541 +/- 27 ng/ml, rbST vs. VEH; p < 0.01). Diameters of DOM or SUB were not affected by immunization or treatment. Concentrations of IGF-I and IGFBP-3 (determined by ligand blot analysis) in FFL from both DOM and SUB were lower (p < 0.05) in GRFi than in HSAi cows. In contrast, IGFBP-2 in FFL was elevated in SUB, but not DOM, in GRFi compared to HSAi cows.(ABSTRACT TRUNCATED AT 400 WORDS)
Stanko
R L
RL
Department of Animal Science, North Carolina State University, Raleigh 27695-7621.
Cohick
W S
WS
Shaw
D W
DW
Harvey
R W
RW
Clemmons
D R
DR
Whitacre
M D
MD
Armstrong
J D
JD
D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000097:blood* / Q000378:metabolism; D002417:Cattle / Q000378:metabolism*; D015237:Dinoprost / Q000494:pharmacology; D005260:Female; D015571:Follicular Fluid / Q000378:metabolism*; D006064:Gonadotropins, Equine / Q000494:pharmacology*; D013006:Growth Hormone / Q000494:pharmacology*; D013007:Growth Hormone-Releasing Hormone / Q000276:immunology / Q000502:physiology; D007114:Immunization; D015151:Immunoblotting; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology / Q000502:physiology; D011994:Recombinant Proteins / Q000494:pharmacology; D012709:Serum Albumin / Q000276:immunology
D002352:Carrier Proteins; D006064:Gonadotropins, Equine; D018969:Insulin-Like Growth Factor Binding Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D012709:Serum Albumin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; C059148:somatotropin releasing hormone (1-29); D015237:Dinoprost