Semen quality deteriorates during the summer. This phenomenon may account at least in part for the reduction in the birth rate during the spring in regions with warm climates.

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Acrylonitrile (ACN) and acrylamide (AA), structurally similar vinyl monomers, are both animal carcinogens. ACN is weakly mutagenic in bacteria and induces sister-chromatid exchange, unscheduled DNA synthesis and cell transformation in cells in culture. AA induces chromosomal aberrations in bone marrow, blood and germ cells in vivo, and dominant lethal mutations in the germ cells of male mice and rats. In the current study, the ability of AA and ACN to induce dominant lethal mutations in the germ cells of male Fischer 344 rats was compared. Three groups of 50 males were gavaged daily for 5 days with ACN (60 mg/kg in normal saline), AA (30 mg/kg in normal saline) or vehicle only; an additional group of 20 males received a single i.p. injection of 0.2 mg/kg triethylenemelamine (TEM) on the afternoon of day 5. Starting 1 day after exposure, each male was bred to one female per week for 4 weeks (TEM-exposed group) or 10 weeks (ACN, AA and control groups). Mating rates were reduced only during week 1 in the TEM-treated group; pregnancy rates were reduced only during week 2 in the AA-exposed group and week 4 in the TEM-treated group. Females were necropsied 13 days after the end of the appropriate mating week and the amount of pre- and post-implantation loss calculated. ACN treatment of male rats induced no increases in either pre- or post-implantation loss in females in any of the 10 weeks post-exposure examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Glyceraldehyde 3-phosphate dehydrogenase-S (GAPDHS) and phosphoglycerate kinase 2 (PGK2), two isozymes restricted to the male germline, catalyze successive steps in the glycolytic pathway in mammalian sperm. Although gene targeting of each isozyme demonstrated that glycolysis is required for normal sperm motility and male fertility, the phenotype of mice lacking GAPDHS is more severe than that of mice lacking PGK2. This study examined sperm function, signaling pathways, and metabolism to investigate factors that contribute to the phenotypic differences between these knockout models. Sperm from the two knockouts exhibited comparable deficits in zona binding, in vitro fertilization with or without zona drilling, and capacitation-dependent tyrosine phosphorylation. In contrast, signaling and metabolic differences were apparent prior to capacitation. Phosphorylation of sperm protein phosphatase 1, which has been associated with the acquisition of motile capacity during epididymal maturation, was deficient only in GAPDHS-null sperm. Carnitine, choline, phosphocholine, and taurine were elevated in sperm from both knockouts immediately after collection from the epididymis. However, only carnitine levels in PGK2-null sperm were significantly different from wild-type sperm, while all four metabolites were significantly higher in GAPDHS-null sperm. We confirmed that glycolysis is required for robust hyperactivation, but found that the motility of PGK2-null sperm improved to levels comparable to wild-type sperm with pyruvate as the sole metabolic substrate. This nonglycolysable substrate did not improve progressive motility in GAPDHS-null sperm. These results identify multiple signaling and metabolic defects that are likely contributors to male infertility and the absence of progressive sperm motility seen in mice lacking GAPDHS.

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