CAUCASIAN VERSUS AFRICAN-AMERICAN DIFFERENCES IN OROSOMUCOID - POTENTIAL IMPLICATIONS FOR THERAPY

We conducted a prospective, nonrandomized study in healthy volunteers to determine if racial differences exist in orosomucoid (ORM) and its variants, and to examine quinidine and lidocaine binding to the protei n. Total ORM serum concentrations were measured by Laurell-Rocket immu noelectrophoresis. Allele types were determined by isoelectric focusin g and immunoblotting. Total and unbound quinidine and lidocaine concen trations were measured with standard fluorescence polarization immunoa ssays after ultrafiltration. The frequency of the common ORM alleles w as similar between 38 Caucasians and 67 African-Americans. Mean total ORM concentration was significantly lower in Caucasians (57.3 +/- 25.4 vs 73.2 +/- 33.9 mg/dl, p=0.01). However, more Caucasians took oral c ontraceptives, which may have decreased ORM concentrations. Quinidine unbound fraction (UF) was related to ORM phenotype. The highest UF was found with ORM 1-S (p=0.009). There were no significant relationships between ORM phenotype and lidocaine UF Overall, African-Americans had higher ORM concentrations than Caucasians. Quinidine binding showed s ignificant relationships to specific ORM variants.