Problem: Mastitis and immunization against constituents of organisms causing mastitis can reduce fertility of cattle and sheep, respectively. For the current experiments, it was hypothesized that these effects are mediated via actions of lipopolysaccharide (LPS), prostaglandin F2α (PGF2), and nitric oxide on oocyte maturation and embryonic development.
Method of study: To evaluate effects on oocyte maturation, oocytes were matured with various concentrations of LPS, PGF2α, or the nitric oxide (NO) generator, sodium nitroprusside (SNP). Following maturation, oocytes were fertilized and cultured until day 8 after fertilization. To test effects on embryo growth, oocytes were matured and fertilized and cultured after fertilization with LPS, PGF2α, or SNP.
Results: Addition of 100 and 1000 ng/mL LPS and 50 and 100 ng/mL PGF2α to oocyte maturation medium reduced the proportion of oocytes that became blastocysts at day 8 after fertilization. When added after fertilization, in contrast, neither LPS nor PGF2α reduced development to the blastocyst stage. Unlike for LPS and PGF2α, addition of SNP during oocyte maturation was without effect on the proportion of oocytes that became blastocysts at day 8 after fertilization. However, addition of 10 μm SNP to culture medium after fertilization completely prevented development to the blastocyst stage while 0.1 and 1 μm SNP did not affect development.
Conclusions: Results indicate that increased local concentrations of LPS, PGF2α, and NO can have deleterious consequences on oocyte function (LPS, PGF2α) and embryonic development (NO). Thus, these molecules are putative mediators of effects of infectious disease or inflammation, including mastitis, on fertility of cattle.