Pii: S0739-7240(00)00084-9

The objective of this study was to examine differences in platelet-activating factor [1-O-alkyl-2acetyl-sn-glycero-3-phosphorylcholine; PAF] in spermatozoa between two lines of Angus beef cattle divergently selected for blood serum insulin-like growth factor I (IGF-I) concentration. Endogenous lipids were extracted from the spermatozoa and endogenous PAF content was determined by radioimmunoassay. The amount of PAF detected in spermatozoa obtained from high IGF-I bulls (n 5 8) ranged from 0.145 to 3.571 pM/10 cells. The level of PAF extracted from spermatozoa obtained from low IGF-Ibulls (n 5 5) ranged from 0.001 to 1.024 pM/10 cells. Polynomial regression analysis revealed a significant cubic relationship (R 5 0.374; F 5 6.292; P , 0.05) between spermatozoa PAF content and blood serum IGF-I concentration. Spermatozoa-derived PAF levels (mean 6 SEM) were significantly higher (P , 0.05) in the high IGF-I group (1.90 6 0.39 pM/10 cells) than in the low IGF-I group (0.59 6 0.20 pM/10 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 spermatozoa but that levels are significantly higher in individuals with high serum IGF-I concentrations. © 2001 Elsevier Science Inc. All rights reserved.