Enzyme inactivation in serum before determination of total bile acids

Endogenous NADH-generating enzymes must be inactivated before total serum bile acids can be measured accurately by the direct enzymic method. To do this, we pretreat the sera with NaOH, in a final concentration of 0.1 mol/L. Consequently, lactate dehydrogenase activity at least as high as 30 000 U/L is destroyed, obviating blank determinations. Values for bile acid in serum, so obtained, agree with values obtained after pretreatment with heat, an alkali-methanol solution, or sodium pyruvate, but our pretreatment has the advantages of ease, speed, economy, and negligible blank values.