Glutathione (GSH), the major low‐molecular‐weight thiol in mammalian cells, is believed to be a necessary factor for the transformation of the disulfide‐stabilized sperm nucleus into the male pronucleus after fertilization. Its concentration in mouse ova, isolated from the ampulla of the oviduct after hormone‐induced superovulation of 3–4‐week‐old mice, has been determined by an enzymic cycling microassay. The level found was 1.80 pmol per ovum. Mean ovum diameter was estimated as 71–72 μm, indicating a GSH concentration of 9–10 mM in the mouse egg. Administration of L‐buthionine S, R‐sulfoximine, an inhibitor of GSH biosynthesis, during the 2 days preceding ovulation, reduced ovum GSH content below 0.20 pmol (<1.0 mM). The mean GSH concentration of the hormone‐stimulated ovaries was reduced from 3.2 mM to 0.2 mM under these conditions. It has also been demonstrated that measurement and manipulation of ovum and ovarian levels of GSH can aid in studying its function in ovaries, ova, and early embryos. Hormone‐induced superovulation was achieved in BSO‐treated prepuberal C57B1/6 X SJL mice whose ovaries contained less than 10% of control levels of GSH. Over 50% of the isolated ova were fertilized in vitro. However, abnormal one‐cell embryos resulted in which the maternally derived pronucleus coexisted with an unchanged sperm nucleus, thus confirming that adequate levels of GSH are necessary for initiating transformation of the fertilizing sperm nucleus.

Summary. Essentially all of the selenium in the rat spermatozoon is bound to a polypeptide of Mr 15 000\p=n-\17000 confined to

Glutathione (GSH), a ubiquitous cysteine-containing tripeptide, is present in high concentration in adult mouse testis (4.3 +/- 0.2 mumol/g). Examination of testis at 0, 7, 14, 21, 28, 35, 42, 50, and 60 days of age reveals that the level of testicular GSH, only 1.4 +/- 0.1 mumol/g in neonates, increases steadily until 28 days of age, when the adult level is reached. An even steeper increase in GSH concentration, when expressed in mumol/mg DNA, is seen between 0 days (0.19 +/- 0.01) and 42 days (1.19 +/- 0.05), at which time the adult level is attained. Enzymatic dissociation of 4-wk-postnatal seminiferous epithelium, using collagenase and dispase either sequentially or in combination, followed by unit gravity sedimentation, yielded maximal GSH concentrations (mumol/mg DNA) in those cell fractions most enriched in pachytene spermatocytes, followed by a second slightly lower peak of activity in the purest round spermatid fraction, which may have lost a significant percentage of its original GSH content. A relatively high GSH content in condensing spermatids, which are at present not isolable without loss of cytoplasm, is implied by the continually increasing levels of testicular GSH/mg DNA between 28 and 42 days of age. It is proposed that retention of GSH is a sensitive indicator of germ cell viability following cell separation procedures. The functions of GSH during meiotic and postmeiotic germ cell development may include protection against mutagens and reduction of disulfide bonds during the processing of cysteine-containing proteins.