Copper is involved in a variety of biological processes such as embryo development, connective tissue formation and nerve cell function. Consequently, copper transport at the cell surface and the delivery of copper to intracellular proteins are critical events in normal physiology (1). The copper transport proteins CTR1 and CTR2 have been identified as possible regulators of cellular copper transport in several cell types (2). However, little is known about the regulation of Cu transport mechanisms in the placenta. We have studied the response of copper transport to Cu deficiency in the human choriocarcinoma cell line b30. The cells were maintained in DMEM supplemented with 10% fetal calf serum and 2% penicillin/ streptomycin. Copper deficiency was induced by the addition of 20μM of the copper chelator diamsar to the medium for 18 hours. Copper uptake was studied using real-time microfluorimetry. Briefly, control or copper-deficient cells on coverslips were loaded with 10μM Phen Green (fluorophore) for 1 hour at 37°C, coverslips were mounted onto the microscope stage and perfused with control Tyrode buffer, cells were exposed to increasing levels of exogenous Cu. Fluorescent quenching (ΔF/cell/min) was measured at 495nm in individual cells using a Nikon Eclipse 2000-U fluorescent microscope and Metaflur software. Protein and mRNA samples were isolated from control and copper-deficient cells and the expression of copper transporters (CTR1/2) analysed by Western and Northern blotting. CTR1 localisation in control or Cu-deficient cells was compared using immunocytochemistry. Copper uptake was increased in copper-deficient cells (Vmax = 128.3±9.96 ΔF/cell/min; mean±SEM)) compared to time-matched controls (48.17±6.05 ΔF/cell/min). However, no difference was seen in Km values. Both CTR1 and CTR2 mRNA levels were significantly (Student’s t test, p<0.05, n = 12) increased by copper-deficiency. CTR1 protein showed both increased expression (p<0.01, n=9) and relocalisation following copper deficiency. We could not measure CTR2 protein levels. These studies demonstrate a compensatory response to Cu deficiency in b30 cells involving increased activity via increased expression of the Cu transporter mechanisms.