Inhibition of the plasma cholinesterase variants by propranolol

The inhibitory effect of (+/-) propranolol 1.69 x 10(-4)-1.69 x 10(-7) mol litre-1 on normal and atypical plasma cholinesterase variants was investigated. The atypical enzyme is less sensitive to inhibition by (+/-) propranolol or either of its enantiomorphs than the usual enzyme. Propranolol 8.45 x 10(-6) mol litre-1 was used as differential inhibitor of 643 plasma samples from individuals of known genotype. Although the measurement of propranolol inhibition alone is not always unambiguous for assigning a definite genotype to a given individual, the correlation of propranolol inhibition with fluoride inhibition gives clear differentiation of the E1uE1u and E1UE1f phenotypes as well as other phenotypes.