Assay of 3-hydroxybutyrate in the picomolar range

A radioisotopic procedure for the assay of 3-hydroxybutyrate is presented. It is based on the measurement of NADH, generated in the 3-hydroxybutyrate dehydrogenase reaction, through the conversion of 2-[U-14C]ketoglutarate to 14C-labeled L-glutamate in the presence of beef liver glutamate dehydrogenase. The assay is linear in the range of 2.5 to 20.0 pmole/sample and about 100-times more sensitive than previous methods. The procedure proved useful for the measurement of 3-hydroxybutyrate in liver samples not exceeding 25 micrograms wet weight.