sodium-bicarbonate and Osteosarcoma

The molecular mechanisms responsible for intracellular pH regulation in the U2-OS osteosarcoma cell line were investigated by loading with 2',7'-bis(2-carboxyethyl)-5(6) carboxyfluorescein ester and manipulation of Cl(-) and Na(+) gradients, both in HEPES- and HCO(3)(-)/CO(2)-buffered media. Both acidification and alkalinisation were poorly sensitive to 4,4'-diisothiocyanate dihydrostilbene-2,2'-disulfonic acid, inhibitor of the anion exchanger, but sensitive to amiloride, inhibitor of the Na(+)/H(+) exchanger. In addition to the amiloride-sensitive Na(+)/H(+) exchanger, another H(+) extruding mechanism was detected in U-2 OS cells, the Na(+)-dependent HCO(3)(-)/Cl(-) exchanger. No significant difference in resting pH(i) and in the rate of acidification or alkalinisation was observed in clones obtained from U-2 OS cells by transfection with the MDR1 gene and overexpressing P-glycoprotein. However, both V(max) and K' values for intracellular [H(+)] of the Na(+)/H(+) exchanger were significantly reduced in MDR1-transfected clones, in the absence and/or presence of drug selection, in comparison to vector-transfected or parental cell line. NHE1, NHE5 and at a lower extent NHE2 mRNA were detected in similar amount in all U2-OS clones. It is concluded that, although overexpression of P-glycoprotein did not impair pH(i) regulation in U-2 OS cells, the kinetic parameters of the Na(+)/H(+) exchanger were altered, suggesting a functional relationship between the two membrane proteins.

Topics: Amiloride; ATP Binding Cassette Transporter, Subfamily B, Member 1; Buffers; Chloride-Bicarbonate Antiporters; Down-Regulation; Fluoresceins; Humans; Hydrogen-Ion Concentration; Osteosarcoma; Protein Isoforms; Sodium Bicarbonate; Sodium Chloride; Sodium-Hydrogen Exchangers; Transfection; Tumor Cells, Cultured

One of the major complications after high-dose methotrexate (HDMTX) infusions is renal damage. We investigated the occurrence of proteinuria after HDMTX administration in children with pediatric malignancies (acute lymphoid leukaemia, osteosarcoma Burkitt's lymphoma). In the period 1989-1990 we gave 52 HDMTX courses to 24 children. During this period, prehydration and extra urinary alkalisation were performed only if the urinary specific gravity was over 1010 or if the urinary pH fell below 7. Using this schedule the mean values obtained for protein extraction were: before the therapy, 0.12 +/- 0.03 g/m2; on day 1 after MTX treatment, 0.38 +/- 0.06 g/m2; and on day 2 after the MTX infusion, 0.39 +/- 0.11 g/m2 (P < 0.01). A significant increase in proteinuria (> 0.2 g/m2 post- vs pretreatment) was detectable in 54% of the patients. In the period 1991-1992 we modified the hydration-alkalisation schedule to include i.v. prehydration for 18-24 h at 3 l/m2/day with a 0.45% NaCl-5% glucose solution along with sodium bicarbonate and posthydration for 72 h with the same solution. On this protocol the mean values determined for the urinary protein content were all in the normal range (pretreatment, 0.03 g/m2/day; day 1, 0.05 g/m2/day; and day 2, 0.08 g/m2/day). These findings were significantly different from the previous results (P < 0.05).

Topics: Adolescent; Bone Neoplasms; Burkitt Lymphoma; Child; Female; Fluid Therapy; Glomerular Filtration Rate; Glucose; Humans; Male; Methotrexate; Neoplasms; Osteosarcoma; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Proteinuria; Sodium Bicarbonate

Following two-compartment kinetic analysis, the effect of loading of transfusion with sodium bicarbonate on methotrexate disposition was investigated in 13 cases with malignant tumor, being treated with high-dose methotrexate. The mean values of total body clearance, when administered at doses 50 mg and 100 mg per kg body weight, were 0.369 and 0.402 (l/h) per kg, respectively. No significant relationship was observed between alpha value and total amount of transfusion, of urine or dosage of sodium bicarbonate. The other kinetic parameters on elimination, beta value, K10 and total body clearance, did not also correlate with those values described above. These results suggest that the elimination profile of methotrexate show linear kinetics, and that massive administration of transfusion with sodium bicarbonate be not necessary if pH value of urine exceeds 7.0.

Topics: Adolescent; Adult; Bicarbonates; Bone Neoplasms; Child; Female; Humans; Hydrogen-Ion Concentration; Infusions, Parenteral; Kinetics; Leukemia, Myeloid, Acute; Lymphoma; Male; Metabolic Clearance Rate; Methotrexate; Neoplasms; Osteosarcoma; Sodium Bicarbonate