Almersjö O

Sequential methotrexate/5-FU: FdUMP formation and TS inhibition in a transplantable rodent colon adenocarcinoma.

SummaryParameters for inhibition of thymidylate synthetase were studied after sequential methotrexate/5-fluorouracil (5-FU) administration in a dimethylhydrazine (DMH)-induced transplantable rat colon carcinoma. Tumor-bearing rats were treated with methotrexate (MTX) 40 mg/kg IP Bolus 5-FU, 100 mg/kg IP, was injected after 24 h. Micromethods for assay of 5-fluoro-2′-deoxyuridylate (FdUMP) and thymidylate synthetase (TS) were used to study the in vivo intracellular pharmacokinetics of 5-FU.Formation of FdUMP was equally rapid in tumors regardless of MTX pretreatment, with peak values found at 30 min. Although MTX pretreatment did not increase peak FdUMP levels, it appeared to result in increased persistence of FdUMP, well in excess of available TS-binding sites, at 24 and 48 h. The combination therapy was less effective in terms of TS inhibition over the first 8 h after 5-FU administration, but may have been associated with improved TS inhibition at later time points.Total levels of TS (TStot) steadily increased from a pre-5-FU treatment level of 18.8 pmol to more than 40 pmol/g at 24 h. MTX per se had no apparent effect on baseline TStot levels or on the 5-FU-mediated increases in TStot.We conclude that MTX and 5-FU were antagonistic in terms of TS inhibition over the first 8 h after 5-FU in this DMH-induced rat colon carcinoma, but were possibly synergistic in increasing persistent levels of FdUMP and TS inhibition at later time points. The observation that 5-FU treatment can result in progressive increases in TS levels in some tumors suggests that this may be an important mechanism of 5-FU resistance.

Regional and systemic serum concentrations of 5-fluorouracil after portal and intravenous infusion: An experimental study in dogs

The serum and urinary concentrations of 5-FU after continuous portal and jugular infusion have been followed by means of a highly sensitive microbiological assay method. Our data indicate that more than 90% of 5-FU was eliminated in the liver after continuous portal infusion of 0.625 mg × kg−1× hr−1,corresponding to a dose of 15 mg × kg−1 ×24 hr−1.Negligible amounts of intact 5-FU were excreted into the bile, and the urinary excretion was only a few percent of the amount infused. The arterial concentration was on average tenfold higher during the continuous jugular infusion than after the continuous portal infusion, indicating that the route of administration has a pronounced effect on the disposition of 5-FU. Twenty-three percent of the jugular dose reached the liver; 77% was degraded by extrahepatic metabolism. Of these, degradation in the prehepatic splanchnic area accounted for 15%.

New assay of 5-fluorouracil in serum by isotachophoresis

Blood levels of 5-fluorouracil are quantitatively determined by isotachophoresis. Serum is deproteinized, purified on an ion-exchange column and concentrated to 20 microliter, and the drug is measured isotachophoretically. Down to 50 pmol (6.5 ng) of the drug can be determined in serum with a methodological error of +/- 6%. The method can be used for routine control of patients undergoing therapy with the drug.

Amino Acid Incorporation into Liver Proteins during Short-Term Ligation of the Hepatic Artery in the Dog

Amino acid incorporation into liver proteins was studied with an in vitro method during and after a short-term hepatic artery ligation (HAL) in the dog. The incorporation of amino a

Inactivation of 5-Fluorouracil by the Liver during Continuous Regional and Systemic Infusion in Pigs

During continuous systemic or portal infusion of 5-fluorouracil (5-FU) to anaesthetized pigs, the cytostatic activity was reduced in blood traversing the liver. The liver eliminated between 15 and 50% of the amount 5-FU given per time unit. During jugular infusion the concentration of cytostatic compounds in portal blood was equal to or less than in systemic blood. The cytostatic activity was much higher in portal blood and lower in systemic blood during portal infusion. The findings speak in favour of portal infusions of 5-FU to patients with disseminated cancer in the liver.

Concurrent allopurinol and 5-fluorouracil: 5-fluoro-2'-deoxyuridylate formation and thymidylate synthase inhibition in rat colon carcinoma and in regenerating rat liver.

SummaryThe formation of FdUMP and the inhibition of TS were studied in a subcutaneously growing transplantable rat colon carcinoma and in regenerating rat liver following bolus administration of 5-FU, with or without HPP pretreatment.In tumor, peak levels of FdUMP at 30 min following bolus 5-FU, 100 mg/kg, averaged 4931±587 pmol/g. Pretreatment with HPP, 50 mg/kg, 24 h and 1 h before 5-FU, reduced the peak FdUMP level to 2085±387 pmol/g. The inhibition of TS by 5-FU treatment was greater than 95% by 30 min, and after 48 h residual enzyme inhibition averaged 40%. No effect on TS inhibition by 5-FU treatment could be observed as a result of HPP pretreatment. The levels of TStot increased linearly after 5-FU treatment and doubled within 48 h.In regenerating rat liver, neither FdUMP levels nor TS inhibition, studied at 1 h after bolus 5-FU, were affected by HPP pretreatment.

Structural and functional changes in ribosomes from ischemic liver in the dog: effects of short-term hepatic artery ligation and hemorrhagic shock.

Structure and function of isolated liver ribosomes from 10 dogs subjected to 1 h of hepatic artery ligation (HAL) or hemorrhagic shock were studied. A shift of polyribosomes to monoribosomes and a decreased capacity to incorporate amino acids into proteins were seen in both experimental conditions. The effects were more pronounced in hemorrhagic shock. Both structural and functional changes were reversible after HAL. In the shock experiments a slight increase of the ribosomal activity was seen after reinfusion but the initial values were not reached during the 2 h after the shock period. Some of the underlying mechanism of altered ribosomal structure and function in liver ischemia are discussed.

General Resorption of Intra Vesically Instilled 5-fluorouracil

To evaluate the resorption of intravesically instilled 5-fluorouracil a single dose of 250 or 1,000 mg. was injected into the empty bladder for 3 hours in 17 patients. The concentration of 5-fluorouracil in serum during instillation was recorded. A microbiologic agar plate method was used for the assay. No measurable 5-fluorouracil concentrations were recorded in the systemic blood of patients with undamaged bladder mucosa and low levels (less than 100 ng./ml. serum) of 5-fluorouracil were found in the systemic circulation of patients with mucosal lesions.

Amino Acid Incorporation into Liver Proteins during Hemorrhagic Shock in the Dog

Liver protein synthesis was studied with an in vitro method during and after 1 h of hemorrhagic shock in the dog. Protein synthesis was significantly decreased already 15 min after induction of hypovolemia and was about 50% of the initial value at the end of the shock period. 2 h following retransfusion, protein synthesis was normalized. Some of the underlying mechanisms leading to decreased protein synthesis in hemorrhagic shock are discussed. Serum concentrations of liver enzymes were unchanged during the shock period indicating that the liver metabolism may be affected without changes in parameters often used to evaluated liver function.