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.
Stanko. R L RL; Cohick. W S WS; Shaw. D W DW; Harvey. R W RW; Clemmons. D R DR; Whitacre. M D MD; Armstrong. J D JD
Key Findings
- Cows immunized against GRF‑1‑29 had lower serum growth hormone and IGF‑I, but higher IGFBP‑2, compared with control cows.
- Administering recombinant bovine somatotropin (rbST) increased IGF‑I levels more in the immunized cows than in controls.
- rbST treatment reduced IGFBP‑2 levels in both immunized and control cows.
- Follicular fluid IGF‑I and IGFBP‑3 were lower in immunized cows, while IGFBP‑2 was higher in subordinate follicles.
Practical Outcomes
- For biohackers, the study suggests that the body can develop antibodies against GRF‑1‑29 that may blunt the GH/IGF‑I axis, potentially reducing the effectiveness of GRF supplementation. It also hints that high doses of external growth hormone can overcome this effect, but the relevance to human dosing is uncertain.
Summary
In a study on cows that were vaccinated against a short piece of the growth‑hormone‑releasing factor (GRF‑1‑29), the animals showed lower natural growth hormone and IGF‑I levels and higher levels of a protein that blocks IGF‑I. Giving them extra growth hormone (somatotropin) raised IGF‑I more in the vaccinated cows and lowered the blocking protein. The findings mainly show how an immune response to GRF can blunt the body’s growth‑hormone system.
Abstract
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)
Study Information
pubmed
1994
10.1095/biolreprod50.2.290