Direct Measurement of Free Copper in Serum or Plasma Ultrafiltrate

Abstract

Copper is an essential element and, under conditions of overload, a toxicant. A dramatic example of copper toxicity is Wilson disease (WD), a treatable but often fatal condition that is difficult to diagnose and monitor. A method for direct measurement of free copper concentrations in serum or plasma ultrafiltrate by inductively coupled mass spectrometry was developed and validated to assist with diagnosis and monitoring WD. The method was shown to be accurate (94%-109% recoveries), linear (0.5-800 microg/dL [0.08-126 micromol/L]), and precise (coefficient of variation, < 15% over the analytic measurement range). A reference interval (0-10 microg/dL [0-1.6 micromol/L]) was determined parametrically with 137 healthy adult (20-59 years) blood donors. No statistically significant difference was observed in males (n = 69) vs females (n = 68). Free copper concentrations for patients diagnosed with WD were at least 6-fold greater than the upper limit of the reference interval before treatment but fell within the reference interval after treatment.

Dynamic internalization and recycling of a metal ion transporter: Cu homeostasis and CTR1, the human Cu+ uptake system

“…Normal serum contains about 1-2 μM total Cu (McMillin et al, 2009) and internalization of CTR1 is caused by an addition as low as 2-5 μM Cu after exposure for 2 h, whereas the response to 20 μM Cu is complete in about 10 min (Molloy and Kaplan, 2009). Cuconcentration-dependence time courses show complex kinetics.…”

Inverse Log-Linear Relationship between Thyroid-Stimulating Hormone and Free Thyroxine Measured by Direct Analog Immunoassay and Tandem Mass Spectrometry

“…One possible reason, demonstrated in this study, is that the IA-FT 4 concentration still remains dependent on both ALB and TBG concentration and therefore may not be a true reflection of free hormone concentration. The ultrafiltration device used in this MS-FT 4 method effectively removes proteins (22 ) and therefore removes protein-bound T 4 from the sample and replaces the dialysis step of the classic equilibrium dialysis method. The protein concentration in the ultrafiltrate is dependent on the filtration device used, temperature, centrifugal force, and time of centrifugation.…”

Rate and Regulation of Copper Transport by Human Copper Transporter 1 (hCTR1)

“…The human copper transporter 1 (hCTR1) 3 gene was discovered by virtue of its ability to complement copper deficiency in yeast Ctr1Ctr3 double mutants, which lack high affinity copper uptake (8). hCTR1 also suppresses phenotypes of copper deficiency in Drosophila CTR mutants (9) and mediates copper transport when expressed in insect cells (10).…”