Insulin-like growth factor-I and insulin-like growth factor binding protein-2 and -5 in equine seminal plasma: association with sperm characteristics and fertility.
The objectives of this study were 1) to determine whether insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding proteins (IGFBPs) were present in seminal plasma of stallions; 2) to compare semen parameters (IGF proteins, sperm numbers, morphology, and motility) from stallions at sexual rest (SR) and when sexually active (SA); 3) to compare semen parameters between stallions with high and low seminal plasma IGF-I concentrations; and 4) to examine the relationship between seminal plasma IGF-I concentrations and fertility parameters of stallions. Ejaculates were collected from stallions at SR (n = 51) and SA (n = 46). Concentrations of IGF-I and IGFBP-2 in seminal plasma samples were determined by radioimmunoassay. Presence of IGFBPs in equine seminal plasma was verified using immunoprecipitation and Western ligand blot procedures. IGF-I, IGFBP-2, and IGFBP-5 were present in equine seminal plasma. Concentrations of IGF-I, IGF-I/protein, total IGF-I, IGFBP-2, IGFBP-2/protein, and total IGFBP-2 were not significantly different (P > or = 0.13) in seminal plasma between stallions at either SR or SA. At SR, stallions with higher seminal plasma IGF-I had more total IGFBP-2 per ejaculate (P < 0.01), more morphologically normal sperm (P = 0.05), and higher first-cycle pregnancy rates (P = 0.02). At SA, stallions with higher seminal plasma IGF-I had fewer cycles per pregnancy (P = 0.02). An association of seminal plasma IGF-I concentration with sperm motility, sperm morphology, and pregnancy rates in bred mares suggests that IGF-I may play a role in sperm function.
Macpherson
M L
ML
Department of Large Animal Clinical Sciences, University of Florida, Gainesville, FL 32610, USA. macphersonm@mail.vetmed.ufl.edu
Simmen
R C M
RC
Simmen
F A
FA
Hernandez
J
J
Sheerin
B R
BR
Varner
D D
DD
Loomis
P
P
Cadario
M E
ME
Miller
C D
CD
Brinsko
S P
SP
Rigby
S
S
Blanchard
T L
TL
D000818:Animals; D015153:Blotting, Western; D005260:Female; D005298:Fertility / Q000502:physiology*; D006736:Horses / Q000502:physiology*; D066298:In Vitro Techniques; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism*; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D011233:Precipitin Tests; D011247:Pregnancy; D011863:Radioimmunoassay; D012621:Seasons; D012661:Semen / Q000166:cytology / Q000378:metabolism*; D013076:Sperm Count; D013081:Sperm Motility / Q000502:physiology; D013094:Spermatozoa / Q000502:physiology*
D018971:Insulin-Like Growth Factor Binding Protein 2; D018975:Insulin-Like Growth Factor Binding Protein 5; D007334:Insulin-Like Growth Factor I