The transport of L-T3 was studied in washed rat erythrocytes. L-T3 uptake was temperature sensitive: the initial velocity of uptake at low substrate concentration was 40 times higher at 37 C than at 0C whereas, at equilibrium, the ratio of cell-associated to extracellular L-T3 was about 7 times lower at 37 C than at 0 C. When [125I]L-T3-loaded erythrocytes were diluted into a serum albumin-containing medium, the efflux of L-T3 proceeded at a rate similar to that of influx. A large excess of unlabeled L-T3 in the medium blocked influx and efflux of labeled L-T3, indicating a saturable carrier-mediated transport process across the plasma membrane. the transport obeyed simple Michaelis-Menten kinetics with an apparent Km of 53 nM and a Vmax of 4.3 pmol/min.10(8) cells at 0 C. The Km increased only slightly with temperature whereas the Vmax was 100 times higher at 37 than at 0 C. The Arrhenius activation energy of uptake was 21 Cal/mol. The nonsaturable adsorption of L-T3 to the cells did not exceed 1% of the equilibrium levels at 0 C and 10% at 37 C. Uptake of L-T3 was very specific: unlabeled L-T4, D-T3, triiodothyroacetic acid, rT3, and DL-thyronine inhibited uptake with inhibition constant (Ki) values which were 35, 60, 65, 110, and 250 times, respectively, greater than the Km of L-T3. [125I]L-T4 uptake was negligible. L-T3 uptake and L-T4 inhibition of L-T3 uptake were pH dependent. It is suggested that only the unionized 4'-OH forms of the hormones were recognized by the transport system. At equilibrium, L-T3 was accumulated within the cell (apparent intracellular concentration approximately 50 times higher than that in the medium at 37 C). However, uptake was not dependent on the transmembrane Na+ gradient, suggesting facilitated rather than active transport. Analysis of L-T3 binding to erythrocyte cytosolic proteins suggested that they were implicated in the intracellular trapping of L-T3. At a concentration of 5 x 10(9) erythrocytes/ml (approximately the blood concentration), the amount of L-T3 accumulated in the cells was 13.5 times higher than the extracellular amount. We conclude that L-T3 is solely transported by a saturable, stereospecific, and Na+-independent carrier system. The intracellular accumulation and the rapid transmembrane movements of L-T3 suggest that erythrocytes might play a role in the interorgan transport of L-T3.

BackgroundExpression of SRY [sex-determining region Y]-box11 (SOX11) is specific to mantle cell lymphoma (MCL) and contributes, in conjunction with immunoglobulin variable heavy chain gene mutation status, to the identification of two forms of this disease.MethodsThe aim of this report was firstly, to design an easy and suitable RT-qPCR method to quantify SOX11 mRNA expression in mantle cell lymphoma and other B cell malignancies with the proper reference gene; secondly, to define the best threshold of relative quantity of SOX11 mRNA in order to reach the best compromise between sensitivity and specificity.ResultsFor best discrimination of MCL and non-MCL groups we determined an area under the curve (AUC) of 0.9750 and a threshold of 1.76 with 100% sensitivity and 88% specificity. AUC and threshold values of respectively 0.91/1.346 [87% sensitivity, 80% specificity] and 0.9525/1.7120 [100% sensitivity, 88% specificity] for GAPDH and RPLP0 respectively denote that the RPLP0 reference gene alone is sufficient for PCR housekeeping gene.ConclusionThis work describes an RT-qPCR assay for SOX11 expression in order to better characterize MCL at diagnosis. Further studies on larger cohorts are needed to evaluate this molecular tool, especially for the follow-up of minimal residual disease.Electronic supplementary materialThe online version of this article (10.1186/s40164-018-0097-6) contains supplementary material, which is available to authorized users.