Development of a highly sensitive and specific two‐site enzyme immunoassay for parathyroid hormone (1‐34): Application to pharmacokinetic study on intranasal parathyroid hormone (1‐34) in human

摘要

A highly sensitive and specific two‐site enzyme immunoassay for parathyroid hormone (1‐34) (PTH(1‐34)) and its usability for the pharmacokinetic study are described. Plasma samples were incubated simultaneously with 2,4‐dinitrophenylated anti‐PTH(1‐34) IgG and anti‐PTH(1‐34) Fab′‐ β‐ ‐galactosidase conjugate. The immune complex formed of the three components was trapped onto (anti‐2,4‐dinitrophenyl group) IgG‐coated polystyrene balls. β‐ ‐ Galactosidase activity bound to the polystyrene balls was assayed by fluorometry. The practical detection limit of PTH(1‐34) was 50 fg (12 amol)/0.05 ml of sample and 1 pg/ml as the concentration and practically no interference occurred by PTH(1‐84) and PTH‐related protein (1‐34) up to 300 pg/ml and 10 ng/ml, respectively. The application of this method has enabled us to directly estimate the bioavailability of PTH(1‐34) dosed intranasaly at the prescribed level (0.090 mg). The pharmacokinetic parameters of the intranasal PTH(1‐34) (n = 4) thus estimated were as follows: the area under the plasma concentration‐time curve (AUC) = 20,500 ± 15,900(SD) pg·min/ml; the mean residence time (MRT) = 194 ± 16.3(SD) min; and the maximal concentration (Cmax) = 98 ± 51(SD) pg/ml with the maximal time (Tmax) = 35.0 ± 12.2(SD) min. J. Clin. Lab. Anal. 12:268–275, 1998. © 1998 Wiley‐Liss, Inc.