Impact of blood serum insulin-like growth factor I on platelet-activating factor in bull spermatozoa

The objective of this study was to examine differences in platelet-activati ng factor [1-O-alkyl-2-acetyl-sn-glycero-3-phosphorlycholine; PAF] in sperm atozoa between two lines of Angus beef cattle divergently selected for bloo d serum insulin-like growth factor I (IGF-I) concentration. Endogenous lipi ds were extracted from the spermatozoa and endogenous PAF content was deter mined by radio-immunoassay. The amount of PAF detected in spermatozoa obtai ned from high IGF-I bulls (n = 8) ranged from 0.145 to 3.571 pM/10(6) cells . The level of PAF extracted from spermatozoa obtained from low IGF-I- bull s (n = 5) ranged from 0.001 to 1.024 pM/10(6) cells. Polynomial regression analysis revealed a significant cubic relationship (R-2 = 0.374; F = 6.292; P < 0.05) between-spermatozoa PAF content and blood serum IGF-I concentrat ion. Spermatozoa-derived PAF levels (mean +/- SEM) were significantly highe r (P < 0.05) in the high IGF-I group (1.90 +/- 0.39 pM/10(6) cells) than in the low IGF-I group (0.59 +/- 0.20 pM/10(6) cells). High IGF-I bulls have a greater than three-fold higher PAF content in their spermatozoa than low IGF-I bulls. The data demonstrate that not only is PAF present in bull sper matozoa but that levels are significantly higher in individuals with high s erum IGF-I concentrations. (C) 2001 Elsevier Science Inc. All rights reserv ed.