The therapeutic effects of orally administered 5'-deoxy-5-fluorouridine, 1-(2-tetrahydrofuryl)-5-fluorouracil and 5-fluorouracil on experimental murine tumors

The antitumor effects of three 5-fluorouracil-related compounds, 5'-deoxy-5-fluorouridine (5'-DFUR), 1-(2-tetrahydrofuryl)-5-fluorouracil (FT-207) and 5-fluorouracil (5-FU) itself, on several experimental murine tumors were compared after oral administration. 5'-DFUR showed strong antitumor activity against the solid type of four kinds of tumors tested with a wide range of effective doses, and also showed moderate antitumor activity against three kinds of solid tumors with a narrow range of effective doses. 5'-DFUR was effective against a few kinds of ascites tumors. In general, the antitumor activity of FT-207 was not very strong, with narrow ranges of effective doses under the present conditions. 5-FU showed strong toxicity but at lower doses its antitumor effectiveness was almost the same as that of FT-207. When the doses were divided into three and the divided dose was given orally three times a day for five consecutive days to mice bearing L1210 leukemia, this modality (with any of the three drugs) enhanced the ILS of the mice by two to three times in the case of the ascites type but not the solid type of L1210. The chemotherapeutic index in oral treatment of the solid type of tumors was higher for 5'-DFUR than for FT-207 or 5-FU. The minimum lethal doses in oral administration for five consecutive days were about 3, 1.5 and 0.5 mmol/kg/day for 5'-DFUR, FT-207 and 5-FU, respectively. In conclusion, 5'-DFUR appeared to have stronger antitumor activity and less toxicity than FT-207 and 5-FU, and it is therefore expected to be clinically useful.

Antitumor polysaccharides from P. ostreatus (Fr.) Quél.: isolation and structure of a beta-glucan

We isolated an antitumor glucan (HA beta-glucan) from the neutral polysaccharide fraction (A3) of a hot-water extract of the edible mushroom P. ostreatus (Fr.) Quél. Purification was accomplished by extractions with 20% sodium chloride solution saturated with thymol and by precipitations with ethanol from dimethyl sulfoxide solution. The glucan showed marked antitumor activity at a dose of 0.1 mg/kg. It is a highly branched (1----3)-beta-glucan having an average structure represented by a pentasaccharide segment consisting of one nonreducing terminal, one 3,6-di-O-substituted, and three 3-mono-O-substituted beta-D-glucopyranosyl residues. This structure was confirmed by examining 13C-n.m.r. spectra taken at 75.46 MHz.

Biopharmaceutical evaluation of methylcellulose as an excipient for nitroglycerin tablets

To examine the bioavailability of nitroglycerin in sublingual tablet, 5 healthy adult volunteers underwent simultaneous sublingual administration of a tablet prepared with methylcellulose and a tablet prepared with lactose containing 0.15 mg of nitroglycerin and 0.15 mg of nitroglycerin-15N3, respectively. In 4 of 5 volunteers, no difference in plasma concentration determined by gas chromatography-mass spectrometry (GC-MS) was observed between 2 tablets described above, so it was well accepted that nitroglycerin in tablets prepared with methylcellulose had a similar bioavailability to that in tablets prepared with lactose. The simultaneous administration of the 2 nitroglycerin tablets to a healthy volunteer, one of which containing the drug labeled with a stable isotope followed by GC-MS assay, seems to be the most suitable method for a precise comparison of bioavailability of the formulations.

Characteristics of the uptake of cysteine-containing leukotrienes by isolated hepatocytes

Leukotrienes were transported into rat hepatocytes by a temperature- and energy-dependent mechanism. The uptake was saturable with high- and low-affinity sites (Km values approx. 1 and 17 microM). Competition and kinetic experiments indicated that leukotrienes C4, D4 and E4 were transported by a common mechanism. The maximal velocity of transport was about 50% higher for leukotrienes D4 and E4 than for leukotriene C4. Leukotriene B4, glutathione disulfide, and the glutathione-S-conjugate of acetaminophen did not interfere with the transport of leukotriene C into hepatocytes. This suggests that the process is specific for cysteine-containing leukotrienes. It is likely that the transport mechanism described here participates in biliary excretion of leukotrienes. This route was previously found to be a major one for elimination of leukotriene C3 in mice and guinea-pigs.

Pharmacokinetics and metabolism of sodium 2-mercaptoethanesulfonate in the rat

The synthetic low-molecular-weight thiol, 2-mercaptoethanesulfonate (mesna), exerts efficient protection against oxazaphosphorine-induced urothelial toxicity by binding the renally excreted and concentrated toxic metabolite(s). In this study, the pharmacokinetics and metabolism of mesna and its disulfide form (dimesna) have been investigated in the intact rat and in several in vitro systems, including isolated perfused organs, freshly isolated cells, and subcellular fractions; the mechanism of reduction of dimesna to form the pharmacologically active thiol mesna has been further studied with purified enzyme preparations. The results may be summarized as follows: (a) After p.o. administration, mesna and dimesna are both absorbed from the intestine, and dimesna undergoes reduction to mesna during intestinal absorption; (b) when present in plasma, mesna is rapidly oxidized to dimesna by a metal-dependent reaction; (c) mesna and dimesna pass unchanged through the hepatic vasculature, are not taken up into liver cells, and are not excreted in bile; (d) in the kidney, dimesna is filtered through the glomeruli and subsequently reabsorbed, whereupon reduction to the pharmacologically active thiol form occurs in the renal tubular epithelium, and the thiol is then reexcreted into the tubular lumen; (e) reduction of dimesna to mesna occurs in intestinal and renal epithelial cells by a mechanism involving the cytosolic enzymes thiol transferase and glutathione reductase. Thus, the formation of the pharmacologically active thiol form from dimesna is associated with the consumption of equimolar concentrations of reduced glutathione.

Renal transport and disposition of Na-2-mercaptoethane sulfonate disulfide (dimesna) in the rat

The transport and reduction of dimesna (Na-2-mercaptoethane sulfonate disulfide) was studied in vitro using isolated, perfused rat kidney, and isolated renal epithelial cells. Cellular uptake of dimesna was found to be dependent on an active transport mechanism working across the luminal brush border, with an app. Km of approximately 22 microM and Vmax approximately 1.4 nmol . 10(6) cells-1 . min-1. Among other low molecular thiols or disulfides reduced glutathione was the only one to exert competitive inhibition. gamma-GT-activity or cellular GSH status had no influence on renal uptake of dimesna, but the intracellular reduction rate was dependent on access to reduced glutathione as a cofactor.

Elevated polyamine content in erythrocytes of malignant lymphoma patients

The polyamine content in erythrocytes was determined in an attempt to establish a biological marker of tumor growth in patients with malignant lymphoma. Erythrocytes from 24 patients with malignant lymphoma and 40 healthy controls were subjected to polyamine determination, using high-performance liquid chromatography. The spermidine and spermine levels in normal human erythrocytes were 15.06 +/- 3.61 and 8.79 +/- 3.12 nmol/10(10) cells, respectively. Spermidine and spermine levels in erythrocytes of lymphoma patients were 14.16 +/- 4.99 and 13.06 +/- 5.37 nmol/10(10) cells in the stage I and II groups, 21.25 +/- 3.80 and 14.17 +/- 6.11 in the stage III groups, and 34.17 +/- 10.37 and 24.39 +/- 16.08 in the stage IV group, respectively. The levels of both polyamines were significantly elevated (P < 0.005) in erythrocytes of stage IV patients, while those of stage I and II patients were within the normal range. Serial studies in 8 patients indicated that the levels of both polyamines in erythrocytes correlated well with the clinincal state. Thus, the determination of polyamines in erythrocytes should be clinically useful to determine the state of progression of malignant lymphoma.

Elevated contents of spermidine and spermine in the erythrocytes of cancer patients

Red blood cells (RBC) from 69 patients with advanced cancer and 37 healthy controls were subjected to polyamine determination by using high-performance liquid chromatography. The polyamine contents in normal human RBC were spermidine 15.04 +/- 3.63 nmol and spermine 8.82 +/- 3.12 nmol per 10(10) RBC. Spermidine and spermine levels in RBC were elevated in patients with cancer (p less than 0.005). Serial studies in seven patients with cancer indicated that both polyamines in RBC were reduced after successful surgery. Our data indicate that the determination of polyamine levels in RBC is clinically useful as a marker of disease activity in patients with cancer.

Myelofibrosis with skin lesions

An elderly male patient with primary myelofibrosis developed many papules on the trunk and later numerous subcutaneous nodules on the face. Histologically these lesions showed the features of extra-medullary haematopoiesis consisting of all the three components, i.e. myeloid, erythroid and megakaryocytic elements, findings never reported in the skin.

Sensitive fluorimetric method for the determination of putrescine, spermidine and spermine by high-performance liquid chromatography and its application to human blood

A fast and sensitive method for the determination of putrescine, spermidine and spermine by high-performance liquid chromatography is described. These compounds are converted to their fluorescent dansyl derivatives and are separated by a reversed-phase chromatographic system (Micropak CH-10) with water and acetonitrile as mobile phase. The sensitivity of the method is 30 pmoles. The application of the method to the determination of polyamines in blood is described. It was found that most of the polyamines circulating in blood are localized in the erythrocytes, their content in normal human blood being spermidine 14.1 +/- 3.1, and spermine 8.4 +/- 2.8 nmoles/ml packed erythrocytes. The polyamine level in serum is less than 0.1 nmole/ml. The polyamine content of the erythrocytes from patients with malignant neoplasms was significantly elevated.