Effects of Glucose and Pyruvate on the Sperm Pene- tration and Fertilization of Mouse Eggs In Vitro

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  • マウス卵子への精子侵入および受精におよぼすグルコースとピルビン酸の影響
  • マウス ランシ エ ノ セイシ シンニュウ オヨビ ジュセイ ニ オヨボス グ

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The present investigation was designed to determine the effects of glucose and pyruvate on the sperm penetration in intact and cumulus-free (denuded) mouse eggs in vitro. The basic medium used for the experiments was a chemically defined medium for the in vitro fertilization of mouse eggs (Toyoda et al., 1971), from which glucose and sodium pyruvate were omitted. Newly ovulated eggs in cumulus clot were obtained from mature females (JCL:ICR strain) treated with 10IU PMSG and 10 IU HCG 48 hr apart. In order to get denuded eggs, the intact eggs were treated with hyaluronidase solution, washed twice and then pooled. Spermatozoa were obtained from the cauda epididymidis of mature males (JCL:ICR strain), suspended into 0.4m1 medium and preincubated at 37°Cunder 5%CO2 in air for 1 hr before being mixed with the eggs. Eggs were examined for evidence of sperm penetration and fertilization 4 to 5 hr after insemination. When only pyruvate (1.0mM) was present in the medium, sperm penetration was never observed in both intact and denuded egg. By contrast, when only glucose (5.56mM) was present in the medium for sperm preincubation and fertilization, 95% of intact eggs were penetrated but only 14% of denuded eggs were penetrated. When pyruvate was present in the medium for sperm preincubation and glucose was present in the medium for fertilization, the rates of sperm penetration were very high in both intact (98%) and denuded (88%) eggs. When glucose was present in the medium for sperm preincubation and pyruvate was present in that for fertilization, the rate of sperm penetration was relatively high (64%) in intact eggs inseminated with spermatozoa prein-cubated for 1 hr, but the fertilization rate was greatly reduced when preincubation time was shortened (6-12 min) or denuded eggs were used. Sperm penetration started immediately after the introduction of glucose into the pyruvate medium containing preincubated spermatozoa and denuded eggs. The rates of sperm penetration at 1, 2, 3 and 4 hr after addition of glucose were 38, 57, 70 and 85%, respectively. These results demonstrate that glucose is needed for the sperm penetration of mouse eggs in vitro even if pyruvate, bovine serum albumin and cumulus cells are present, while pyruvate is necessary for the maintenance of the fertilizability of the gametes. It is considered that glucose acts on the final stage of sperm capacitation or on the gamete interaction during sperm penetration of zona pellucida.

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