Erythropoietin alters the pharmacokinetics of organic anions mainly eliminated by the kidney in rats.

Erythropoietin (EPO) is a cytokine originally used for its effects on the hematopoietic system, and is widely prescribed around the world. In the present study, the effects of EPO administration on p-aminohippurate (PAH, a prototype organic anion) pharmacokinetics and on the renal expression of PAH transporters were evaluated. Male Wistar rats were treated with EPO or saline (control group). After 42 h, PAH was administered, and plasma samples were obtained at different time points to determine PAH levels. PAH levels in renal tissue and urine were also assessed. The renal expression of PAH transporters was evaluated by Western blotting. EPO-treated rats showed an increase in PAH systemic clearance, in its elimination rate constant, and in urinary PAH levels, while PAH in renal tissue was decreased. Moreover, EPO administration increased the expression of the transporters of the organic anions evaluated. The EPO-induced increase in PAH clearance is accounted for by the increase in its renal secretion mediated by the organic anion transporters. The goal of this study is to add important information to the wide knowledge gap that exists regarding drug-drug interactions. Owing to the global use of EPO, these results are useful in terms of translation into clinical practice.

Time evolution of methotrexate-induced kidney injury: A comparative study between different biomarkers of renal damage in rats.

Methotrexate (MTX) is commonly used in the treatment of malignant diseases and autoimmune and chronic inflammatory disorders. Along with its effective therapeutic power, MTX has adverse effects on the kidneys. Discovery of new biomarkers is required to improve the early detection of renal damage and optimize the effectiveness of treatments. The aim of this study was to evaluate the time course of MTX-induced nephrotoxicity and to compare the urinary excretion of the organic anion transporter 5 (uOat5) with alterations in other markers of renal function, and to elucidate the possible molecular mechanisms involved in uOat5. Animals were exposed to a unique dose of MTX (80 mg/kg body weight, intraperitoneal). Experiments were carried out at days 2, 4, 8 or 14 after MTX administration. Markers of renal damage, such as creatinine and urea plasma levels, urinary activity of alkaline phosphatase, microalbuminuria, urinary excretion of neutrophil gelatinase-associated lipocalin (uNGAL) and histopathology, were evaluated. Renal organic anion transporter 5 (Oat5) expression and its presence in different urine fraction were assessed by western blotting. uOat5 was significantly increased 2 days after MTX treatment, before than any alteration in other parameters of kidney injury or renal morphology occurred. uNGAL showed an inverted pattern of urinary excretion compared to uOat5. Exosomal pathway is involved in the urinary excretion of Oat5 and depends on the degree of damage induced by MTX. These experimental data allow proposing uOat5 as a potential non-invasive biomarker for early detection of MTX-induced nephrotoxicity.

Time course effects of methotrexate on renal handling of water and electrolytes in rats. Role of aquaporin-2 and Na-K-2Cl-cotransporter.

Methotrexate (MTX) is a derivate of folic acid, commonly used as an anchor drug for the treatment and management of malignant diseases and autoimmune disorders. However, nephrotoxicity is an important drawback of MTX therapy. Unfortunately, there are not enough studies reporting the nature of the renal failure induced by MTX. Thus, the aim of this study was to evaluate the time course of renal handling of water and electrolytes in male Wistar rats, after the exposure to a unique dose of MTX (80 mg/kg b.w.). Experiments were carried out at day 2, day 4, day 8 and day 14 after MTX administration. Several parameters of kidney function related to water and electrolytes handling were evaluated. Renal expression and urinary excretion of aquaporin-2 (AQP2) and Na-K-2Cl-cotransporter (NKCC2) were determined by Western blotting. MTX produced alterations on water handling on the second day after treatment, showing a significant increase in solute free water reabsorption which might be mediated by the increased expression of AQP2 in apical membranes. On the other hand, MTX produced alterations on electrolytes handling on the fourth day after treatment, showing a significant decrease of sodium chloride excretion, mediated at least in part, by the increase renal expression of NKCC2. These results provide valuable information to clinical practice in order to be able to find therapeutic targets that diminish adverse effects and health deterioration. Moreover, MTX treatment altered AQP2 and NKCC2 urinary excretion allowing postulating these transporters as potential biomarkers of MTX induced nephrotoxicity.

Impact of the induced organic anion transporter 1 (Oat1) renal expression by furosemide on the pharmacokinetics of organic anions.

AIM: Furosemide is a loop diuretic. Different authors demonstrated that continuous administration of furosemide modulates the expression of organic anion transporters. This study was undertaken to simultaneously evaluate the effects of furosemide pretreatment on organic anion transporter 1 (Oat1) and multidrug resistance protein 2 (Mrp2) renal expressions, on p-aminohippurate (PAH) pharmacokinetics and on renal and urinary PAH levels in rats. METHODS: Male Wistar rats were treated with furosemide (6 mg/100 g body weight per day, subcutaneously, 4 days) (treated group) or saline (control group). On the fifth day, PAH was administered as a bolus infusion in the femoral vein, and plasma samples were obtained from femoral artery at different time points. PAH levels in renal tissue and urine were also assessed. Renal Oat1 and Mrp2 expressions were evaluated by western blotting. RESULTS: Furosemide pretreatment increased both the expression of Oat1 and Mrp2. PAH plasma concentrations decreased following a biexponential function. The furosemide-treated group showed higher PAH plasma levels, a lower systemic clearance and elimination rate constant from the peripheral compartment, indicating that PAH renal elimination was decreased. PAH levels in renal tissue were significantly elevated and in urine appeared to be significantly lower as compared with control animals. CONCLUSIONS: Furosemide pretreatment caused a significant decrease of PAH renal elimination, despite Oat1 and Mrp2 augmented renal expression. The goal of the present study is the addition of important information in the wide gap of knowledge that exists about drug-drug interactions. Because of furosemide worldwide use, the data obtained are interesting and useful in terms of translation to clinical practice.