A specific method for the quantitative determination of
biocytin from urine of
biotinidase deficient patients is described using HPLC-separation and quantitative determination by an
avidin binding method. Partial purification of
biocytin from urine was achieved with an
anion exchange resin and concentration of the eluate by lyophilization. The recovery of
biocytin from urines was 95.3 +/- 5.9 (mean +/- SD). The precision of
biocytin estimation in patients urines including the HPLC-sample preparation procedure varied between 5.9% and 10.5% (CV).
Biocytin concentrations were measured in urine samples of 5 patients obtained during and/or before
biotin therapy. Before treatment
biocytin excretion ranged from 6.2-28.8 nmol/mmol
creatinine. During
therapy biocytin excretion increased to the 1.3 to 4-fold level in 3 out of 4 patients. However, there was no dose-related increase of
biocytin excretion when pharmacological doses were administered. Apart from
biocytin and
biotin, patients excrete additional
biotin derivatives. Some of these have been preliminary identified as
bisnorbiotin and oxidation products of
bisnorbiotin,
biocytin and
biotin.