In vitro induction of acrosome reactions in stallion spermatozoa by heparin and A23187.
The ability of the glycosaminoglycan, heparin, and the calcium ionophore, A23187, to induce acrosome reaction in equine spermatozoa was assessed using semen from 3 warmblood stallions of known high fertility. After collection of semen, the spermatozoa were washed and incubated in vitro with heparin or A23187. Incubation periods were 0, 4, 6 or 8 h with 0, 1, 10 or 100 microg/ml heparin or 0, 10, 30 or 60 min with 0, 0.01, 0.1, 1 or 10 microM A23187, respectively. Acrosome reactions were determined by staining the spermatozoa with naphthol yellow S plus erythrosin B, and sperm viability was assessed by eosin B-nigrosin staining. Both stains were evaluated under bright-field illumination at x 1000 magnification. Maximal percentages of acrosome reactions were found to occur after incubation for 4 h with 100 microg/ml heparin (71.8 +/- 3.5 % acrosome-reacted spermatozoa compared with 18.7 +/- 1.1 % in control spermatozoa; P < 0.001) or with either 1 or 10 microM A23187 for 60 min (44.0 +/- 6.2 and 45.3 +/- 5.0 % acrosome reacted spermatozoa, respectively, compared with 17.8 +/- 1.5 % in the controls, both P < 0.01). Maximal responses to these conditions varied significantly between stallions (P < 0.01). These results indicate that acrosome reaction can be successfully induced in vitro in stallion spermatozoa with both heparin and A23187, a possible basis for the laboratory prediction of fertility in this species.
Christensen
P
P
Hampshire Cattle Breeders Society, Ltd., Beechen Lane, Lyndhurst, Hampshire, SO43 7NN, UK.
Whitfield
C H
CH
Parkinson
T J
TJ