Multiple drug-resistant gene 1 in children with steroid-sensitive nephrotic syndrome

Background: A full dose of corticosteroid is required to induce complete remission (CR) in steroid‐sensitive nephrotic syndrome (SSNS), unless it is possible to taper and discontinue along with the course after CR. But the mechanism of this change in steroid sensitivity remains unknown. P‐glycoprotein (PGP) can eliminate given corticosteroids from cytoplasm, which results in corticosteroid resistance. Therefore, drug delivery was analyzed using real‐time polymerase chain reaction (PCR) of multiple drug‐resistant gene 1 (MDR1; encoding PGP) mRNA expression. Methods: Fourteen patients with SSNS (male/female: 14/0; age: 1–23 years; mean 10.4 years) were enrolled in the study. MDR1 mRNA gene expression of peripheral blood nucleated cells (PBNC), before and after CR (19 sets of blood samples), was quantified using real‐time PCR. Results: The MDR1 mRNA levels before CR were variable in each patient, but there was an apparent decrease in the MDR1 gene expression of PBNC after CR (P