Measurement of enolase molecules in the single preimplantation rat embryo by an enzyme lmmunoassay system

The amount of enolase (EC 4.2.1.11) molecules in a single preim-plantation rat embryo was determined by an enzyme immunoassay system. An advantage of this assay system is its ability to distinguish each isozyme (αα, αγ and γγ forms) by using the specific antisera to a and y subunits. The isozyme of enolase was mostly the aa form through one-cell to blastocyst stages, whereas the αγ and γγ forms were scarcely detected. Since the immunoassay system is highly sensitive, the minimum amount detectable being 1 amol(1 × 10⁻¹⁸ mole), the amount of aa form enolase could be determined in single embryos in all preimplantation stages. The results have revealed that the amount of aa form enolase molecules does not change through one-cell to morula stages, but increases remarkably between morula and blastocyst stages.