Exposure of human, boar, or bull sperm to a synthetic peptide increases binding to an egg-membrane substrate

We evaluated the effects of in vitro exposure of sperm to synthetic FertPlu s(R) peptide, which represents a 60-amino acid sequence within rat prosapos in, using a microwell sperm-binding assay (SBA), in which an extract of hen 's egg served as the binding substrate. Sperm suspensions were incubated wi th FertPlus(R) peptide (six to eight concentrations; 0 and 20-1,280 pM) at 37 degrees C for 10 minutes, diluted greater than or equal to 20 times, and placed onto SEA plates. After 60 minutes at 37 degrees C, unbound sperm we re washed away and the DNA of bound sperm was quantified. Percentage of spe rm bound was independent of the percentage of motile sperm, but immotile sp erm did not bind. For fresh human sperm (25 ejaculates), the percentage of sperm bound was increased by exposure to 640 pM peptide (P < 0.01). For 11 of 25 samples, the percentage of sperm bound for the aliquot exposed to 640 pM peptide was greater than or equal to 1.4 times the value for a 0 pM con trol aliquot. With frozen-thawed human sperm, for six of seven samples, bin ding was greater than or equal to 1.4 times greater after exposure to 640 p M peptide. For boar sperm held far similar to 24 hours at similar to 18 deg rees C before use (28 ejaculates), there was a higher percentage of sperm b ound for aliquots previously exposed to 1,280 pM peptide than there was for control aliquots (P < 0.01). For 16 of 28 samples, exposure to peptide inc reased the percentage of sperm bound by greater than or equal to 1.4 times. For frozen-thawed bull sperm, percentage of sperm bound was greater than o r equal to 1.4 times greater for 4 of 10 samples that were briefly exposed to 160 pM peptide. Clearly, human, boar, and bull sperm were beneficially m odified by brief in vitro exposure to FertPlus(R) peptide, so that for many samples a greater percentage of sperm was bound in vitro. As presented in an accompanying paper, fertility of bull sperm was increased by brief expos ure to FertPlus(R) peptide.