1H-NMR spectra of ethanol extracts of oocytes. a Sham incubation (i.e., oocytes not exposed to NH3/NH4+). b Oocytes incubated with 0.5 mM 15NH3/15NH4+ for 10 min. Each spectrum represents the extract of 20 oocytes. TSP, 3-trimethylsilyl-[2,2,3,3-d4]-propionate(Na+), was added as a chemical-shift reference (0.0 ppm). *Glycine was added during oocyte extraction to serve as an internal concentration standard and to control for potential metabolite losses. **Residual ethanol contaminant remaining after extraction. Estimated concentrations of metabolites in control noninjected oocytes not exposed to NH3/NH4+. (A) Glutamate (Glu): 6.48 mM. Estimated metabolite concentrations after incubation with 15NH3/15NH4+ for 10 min: Glu: H2O, 1.69 mM. Glutamine (Gln): 1.1 mM. Glu and Gln methylene protons (H4 and H3) and lactate methyl protons (H3) are depicted. Glu H4 and H3 were observed in control noninjected oocytes incubated with 15NH3/15NH4+