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Biomedical subjects

J Lankelma

Publications and source records attributed to J Lankelma.

At least 91 records · Page 5Linked to original sources
PubMed1987

Potentiation of doxorubicin cytotoxicity by the calcium antagonist bepridil in anthracycline-resistant and -sensitive cell lines. A comparison with verapamil.

The ability of the calcium channel blocker bepridil (Bp) to potentiate doxorubicin (Dx) cytotoxicity and enhance its accumulation in anthracycline-sensitive and -resistant human ovarian carcinoma cells (A2780 and 2780AD) and Chinese hamster ovarian (CHO) cells (AUXB1 and CHRC5) was compared with that of verapamil (Vp). A continuous exposure (48-72 h) to Bp as well as Vp potentiated Dx cytotoxicity in 2780AD cells. In short-term incubations (2 h Dx and 4 h calcium channel blocker) the same effects were observed: 4 microM Bp (4Bp) and Vp (4Vp) were equipotent, but at concentrations of 1 and 2 microM, Vp was more active (4Vp = 4Bp greater than 2Vp greater than 2Bp greater than 1Vp greater than 1Bp). In CHRC5 cells the corresponding sequence was: 4Vp greater than 4Bp greater than 2Vp greater than 2Bp greater than 1Vp greater than 1Bp. At high (marginally inhibitory) concentrations, Bp and Vp reversed Dx resistance completely in CHRC5 cells and partly in 2780AD cells. No significant potentiation of Dx cytotoxicity by Bp or Vp was found in A2780 cells, but both were active in AUXB1 cells. In studies with radiolabelled Dx (2 microM), Bp and Vp (16.5 microM) stimulated accumulation in CHRC5 cells almost up to the level in AUXB1 cells. Dx accumulation in 2780AD cells (52 pmol/10(6) cells) could be stimulated to a maximum of about 90 pmol/10(6) cells (drug level in A2780 cells was 153 pmol/10(6) cells). Also, Bp- and Vp-induced stimulation of Dx accumulation was observed in AUXB1, but not in A2780 cells. Bp effected a dose-dependent inhibition of Dx efflux from preloaded 2780AD cells, but not from A2780 cells. We conclude that Bp is more effective than Vp in reversing resistance when both compounds are used in vitro at concentrations which are clinically achievable in plasma.

Bepridil↗
PubMed1987

Unchanged pharmacokinetics of VP-16-213 (etoposide, NSC 141540) during concomitant administration of doxorubicin and cyclophosphamide.

In patients with small-cell lung cancer VP-16-213 is often given in combination with doxorubicin and cyclophosphamide. Little is known about possible interactions between these drugs. Therefore we investigated in 7 patients the pharmacokinetics of VP-16-213, with and without the other two drugs. We found no change in the pharmacokinetics. We also provide evidence that the pharmacokinetics did not change in two sequential administrations of the drug. Pharmacokinetic data are in agreement with previous reports.

Aged↗
PubMed1987

Daunomycin accumulation in resistant tumor cells as a screening model for resistance modifying drugs: role of protein binding.

A potential screening system for drugs that modify anthracycline resistance was investigated. The effect of the calcium antagonistic agents verapamil, diltiazem, bepridil and Ro 11-2933/001 on daunorubicin (DNR) accumulation in the doxorubicin resistant cell line 2780AD was measured. For this purpose cells were suspended in medium with varying concentrations of bovine serum albumin (BSA) and in human plasma to establish the influence of protein binding on DNR accumulation. Increase of protein concentration did not affect DNR accumulation when no calcium antagonists were present but caused an increase in concentrations of calcium antagonists needed to promote DNR accumulation. It appeared that DNR accumulation in suspended cells correlated well with cytotoxicity assays, performed on cells growing in monolayer in 96-well microtiter plates, when accumulation was measured in medium with the same protein constitution as in growth medium (10% fetal calf serum). It is concluded that protein binding effects should be taken into account in the screening of compounds for the circumvention of multidrug resistance.

Antibiotics, Antineoplastic↗
PubMed1987

Effect of pyrimidine nucleosides on body temperatures of man and rabbit in relation to pharmacokinetic data.

The effect of high-dose uridine on body temperatures of rabbits and man has been studied in relation to plasma concentrations of uridine and its catabolite uracil. Uridine induced fever in both rabbits and man. High-dose cytidine had no influence on body temperature in rabbits. Plasma concentrations of uridine were between 1 and 1.5 mM at 30 min after an iv bolus injection of 400 mg uridine/kg in rabbits and reached peak levels of 2 mM after a 1-hr infusion of 12 g uridine/m2 in man. The plasma concentration of cytidine in rabbits was about 0.5 mM and that of uridine was 0.30 mM at 30 min after an iv bolus injection of 400 mg cytidine/kg. The mean residence time for uridine in patients and rabbits varied between 80 and 195 min. The area under the plasma concentration-time curve (AUC) for uridine in rabbits was 2.0 mmol.hr/liter, and that for cytidine was 0.6 mmol.hr/liter. A large AUC for uridine indicates a prolonged exposure of tissues to uridine, which might lead to extensive formation of degradation products. The administration of some of these catabolites, dihydrouracil (at 20-40 mg/kg), carbamyl-beta-alanine (at 60 mg/kg), and beta-alanine (at 300-400 mg/kg), resulted in a significant increase in body temperature. It is concluded that the change in body temperature associated with uridine administration was not due to bacterial pyrogens but that one of the degradation products might be involved in thermoregulation.

Animals↗
PubMed1986

Analysis of doxorubicin, 4'-epidoxorubicin, and their metabolites by liquid chromatography.

An analytical method based on isocratic HPLC separation and fluorescence detection was developed to allow for sensitive and specific analysis of anthracyclines and their metabolites in plasma and urine. The method is particularly advantageous when comparing the metabolism and/or pharmacokinetics of analogues, such as doxorubicin [(8S, 10S)-10-[(3-amino-2,3,6-trideoxy-alpha-L-lyxo-hexopyranosyl)- oxy]-8-glycolyl-7,8,9,10-tetrahydro-6,8,11-trihydroxy-1-meth- oxy-5,12-naphthacenedione] (1) and 4'-epidoxorubicin (2), since both drugs and their metabolites can be analyzed under identical conditions. The analytical properties of 1, 2, and eight metabolites were studied in plasma, serum, buffer solution, and urine. The detection limit in plasma was 4 X 10(-8) M for the glucuronides, 7 X 10(-9) M for the glycosides, and 1 X 10(-9) M for the aglycones. In plasma, 1, 2, doxorubicinol (3), 4'-epidoxorubicinol (4), doxorubicinone (5), and doxorubicinol aglycone (6) showed a linear concentration-response relationship from their detection limit up to 5 X 10(-6) M. A linear calibration graph for plasma samples was also obtained for 7-deoxydoxorubicinone (7) and 7-deoxydoxorubicinol (8); however, these compounds had a significantly lower upper limit (5 X 10(-7) M). Urine samples were acidified to pH 2.5 and analyzed by HPLC without further purification. A linear calibration curve was obtained in the clinically relevant range. The detection limit in urine was approximately 5 X 10(-8) M. Plasma and urine of two patients who had received 4'-epidoxorubicin by iv bolus injection were analyzed.

Chromatography, High Pressure Liquid↗
PubMed1986

Sensitivity of human, murine, and rat cells to 5-fluorouracil and 5'-deoxy-5-fluorouridine in relation to drug-metabolizing enzymes.

Six cell lines differing in histological origin were studied regarding the growth inhibitory effect of fluoropyrimidines in relation to their metabolism. The human colon carcinoma cell line WiDr was most sensitive to 5-fluorouracil (FUra) (50% growth inhibitory concentration, 0.7 microM) and to its analogue 5'deoxy-5-fluorouridine (5'dFUR) (50% growth inhibitory concentration, 18 microM). The murine B16 melanoma cell line was moderately sensitive to FUra but least sensitive to 5'dFUR. The 50% growth inhibitory concentration values in the human melanoma cell lines IGR3 and M5, the transformed human intestine cell line intestine 407 and the rat hepatoma cell line H35 varied for FUra between 1.7 and 5.0 microM, and for 5'dFUR between 54 and 160 microM. Several enzymes from pyrimidine metabolism responsible for FUra metabolism were measured with FUra as a substrate. The activity of uridine phosphorylase, which catalyzes the conversion of 5'dFUR to FUra, was lowest in B16 cells correlating with the low sensitivity to 5'dFUR. When adenosine 5'-triphosphate was included in the reaction mixture for uridine phosphorylase, FUra was rapidly channeled into FUra nucleotides via its nucleoside. The rate of channeling appeared to correlate with the nucleoside phosphorylase activity in the various cell lines. In several cell lines activities of nucleotide-degrading enzymes were rather high and interfered with the measurement of orotate phosphoribosyl transferase (OPRT) with FUra as substrate. Addition of the phosphatase inhibitor glycerol-2-phosphate partly prevented breakdown of the newly formed 5-fluorouridine 5'-monophosphate and enabled measurement of OPRT. The WiDr cell line had a relatively high OPRT activity which could explain its sensitivity to FUra. The activity of thymidylate synthase was measured at a suboptimal concentration of 1 microM and at the optimal concentration of 10 microM deoxyuridine 5'-phosphate. With all cell lines the ratio between the activities at 10 and 1 microM was between 2.3 and 3.6. The activity of thymidylate synthase was lowest in WiDr and IGR3 cells and 3-4 times higher in M5 and Intestine 407 cells. The inhibition of 0.01 microM 5-fluorodeoxyuridine 5'-monophosphate was 80-90% at 1 microM deoxyuridine 5'-phosphate and 50-70% at 10 microM deoxyuridine 5'-phosphate with all cell lines. At 0.1 microM 5-fluorodeoxyuridine 5'-monophosphate enzyme activity was inhibited by 95-100%. The incorporation of FUra into RNA was relatively low in IGR3 cells and 3-5 times higher in all other cell lines.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Highly sensitive determination of 5-fluorouracil in human plasma by capillary gas chromatography and negative ion chemical ionization mass spectrometry.

A sensitive method using gas chromatography and electron-capture negative ion mass spectrometry for the determination of 5-fluorouracil in plasma is described. 5-Chlorouracil was used as internal standard. Sample clean-up consisted of extraction of the 5-halogenated uracil derivatives with 2-propanol--diethyl ether (22:78, v/v) at pH 6, followed by a back-extraction into aqueous buffer at pH 10.5. Pentafluorobenzyl derivatives of 5-fluoro- and 5-chlorouracil were prepared by extractive alkylation with pentafluorobenzyl bromide with dichloromethane as solvent and tetrabutylammonium as counter-ion. The limit of sensitivity employing this technique was 50 fg on-column. Quantitation in human plasma was possible down to 3 X 10(-9) M (0.39 ng/ml). Mass fragmentographic analysis of 5-fluorouracil in plasma of patients after a bolus injection of 500 mg/m2 is presented. Plasma concentrations could be determined for at least 8 h after administration.

Alkylation↗
PubMed1984

Separation of several 5-fluorouracil metabolites in various melanoma cell lines. Evidence for the synthesis of 5-fluorouracil-nucleotide sugars.

5-Fluorouracil (5FU) metabolism was studied in intact cancer cells kept in suspension by incubation with tritiated 5FU. Metabolites were analyzed using various chromatographic procedures, including a one-directional separation on PEI-cellulose sheets, which separated 5FU from the mono-, di- and triphosphate forms and from nucleotide sugars. The monophosphate ester was present as FdUMP, as could be demonstrated with another chromatographic procedure. In the human melanoma cell lines IGR3 and M5 the main metabolite of 5FU was 5-fluorouridine, while in the murine B16 melanoma only a small amount of 5-fluorouridine was formed. In B16 cells more 5FU label was present as the triphosphate ester while in M5 cells more FdUMP was formed. With all three cell lines 5FU was incorporated into RNA; this incorporation was stimulated by 1 mM N-(phosphonacetyl)-L-aspartate (PALA). PALA did not significantly affect the conversion of 5FU into other metabolites, nor did it affect the incorporation of 5FU into DNA. A 5FU-nucleotide sugar, present as the diphosphate-glucose, was a predominant 5FU-metabolite in M5 cells but not in the other cell lines. Its identity was confirmed by thin-layer chromatography and high-performance liquid chromatography. Its possible function is discussed.

Animals↗
PubMed1984

Pharmacokinetics of carminomycin in man: biweekly schedule vs single dose every three weeks.

Carminomycin was administered to five patients at a dose of 7.5 mg/m2 twice weekly. Plasma and urine samples were obtained during two subsequent 72-hr periods following drug administration, and assayed for carminomycin (C) and carminomycinol (Col) by HPLC with fluorescence detection. Distribution of carminomycin was rapid and drug levels decreased below the detection limit (5 X 10(-9)M) within 24 hr. Carminomycinol appeared very quickly and surpassed carminomycin levels in 10 min-4 hr, disappearing very slowly, with a half-life of 40-98 hr. No major differences in pharmacokinetic behavior were found when comparing the five patients in this study with patients who received 18 mg/m2, as described in a previous report. After the second dose of carminomycin in the 7.5 mg/m2 twice weekly schedule, however, carminomycin pharmacokinetics were found to be altered in comparison with the first dose, the most pronounced difference being an increase in the t1/2 for Col from 65 +/- 28 to 173 +/- 81 hr.

Adult↗
PubMed1984

Phase I and pharmacokinetic studies of high-dose uridine intended for rescue from 5-fluorouracil toxicity.

The clinical effects and pharmacokinetics of high-dose uridine were determined in seven patients with advanced-stage cancer and in one healthy volunteer. Uridine was also examined for its effect on 5-fluorouracil toxicity in two patients. Uridine was administered as a 1-hr i.v. infusion at doses of 1 to 12 g/sq m. Plasma and urine samples were analyzed for uridine and uracil using high-pressure liquid chromatography. In 23 courses of uridine alone, the only toxicity observed was transient shivering after one of two courses at 12 g/sq m. This side effect was also seen after administration of uridine (10 g/sq m) during combination with 5-fluorouracil. The pretreatment plasma uridine concentration was elevated from low micromolar to millimolar levels with uridine administration at doses up to 12 g/sq m. Maximal areas under the concentration-time curve were about 5 mmol/liter/hr. Both peak plasma level and area under the curve for uridine increased linearly with dose. Uridine plasma decay curves were biphasic with a terminal half-life of 118 min. Half-life, volume of distribution (634 ml/kg), and total clearance (4.98 ml/kg/min) appeared to be independent of dose. Plasma uracil concentration increased gradually after administration of uridine to plateau levels. Maximal plasma uracil concentrations were about one-tenth that of peak uridine concentrations. The plasma uracil level declined with a half-life of about 40 min after uridine levels decreased to 300 microM. Total urinary excretion of uridine was 24% of the dose, while the amount of uracil recovered in urine was 3.4%. In two patients, uridine rescue was attempted during 5-fluorouracil dose escalation. Uridine at 5 to 6 g/sq m given on 1 or on 2 days after 5-fluorouracil did not prevent myelosuppression and gastrointestinal toxicity associated with increasing plasma concentrations of 5-fluorouracil. These data show that uridine administered as a 1-hr infusion at doses which provide peak plasma uridine concentrations in the millimolar range is well tolerated. Rapid elimination of uridine primarily due to catabolism results in modest exposure to substantially elevated plasma uridine concentrations. Preliminary findings suggest that prolonged treatment with uridine may be required to test its potential to rescue patients from 5-fluorouracil toxicity.

Adult↗
PubMed1983

Pharmacokinetics of 4'-epi-doxorubicin in man.

The pharmacokinetics of 4'-epi-doxorubicin (4'-epi-adriamycin, 4'-epi-DX) in man can be described by a three-compartment model with a rapid distribution phase and a very long elimination phase. Urine excretion amounts to a total of about 11% of the administered dose during 48 h after drug administration, and less than 1% during the following 48 h. In plasma 4'-epi-doxorubicin is rapidly converted to five metabolites (4'-epi-doxorubicinol, aglycones and glucuronides), the concentration of the aglycones sometimes exceeding that of 4'-epi-DX. In urine only three metabolites were found in addition to the parent drug; they were identified as 4'-epi-doxorubicinol (EOH), 4'-epi-doxorubicin-glucuronide (E-Glu) and 4'-epi-doxorubicinol-glucuronide (EOH-Glu). Comparison of the pharmacokinetics and metabolic profiles of 4'-epi-DX and doxorubicin (DX) in man revealed that 4'-epi-DX eliminates faster than DX.

Chromatography, High Pressure Liquid↗
PubMed1982

Plasma concentrations of carminomycin and carminomycinol in man, measured by high pressure liquid chromatography.

In 9 patients with advanced malignant disease who received carminomycin (CMM) in an i.v. bolus injection (dose 18 mg/m2), curves of plasma concentrations of CMM and carminomycinol (CMMOH), a metabolite, versus time were constructed. For determination of plasma concentrations, high pressure liquid chromatography was used. For CMM and CMMOH the median areas under the curves (AUC's) were 31 (range 4-57) X 10(-8) mol/Ql/hr (measured over 24 hr) and 100 (range 309-158) X 10(-8) mol/l/hr (measured over 48 hr) respectively. From the data an accumulation of CMMOH in patients receiving treatments separated by brief intervals ban be predicted (half-life time of plasma disappearance for CMMOH was 2 days). Clinical toxicity was lowest in those 3 patients showing the lowest AUC for both CMM and CMMOH.

Breast Neoplasms↗
PubMed1981

Determination of thioproline in plasma using high performance liquid chromatography.

The determination of thioproline in plasma of cancer patients, using high performance liquid chromatography (HPLC) is reported. As column support, a silica-bonded cation exchanger was used. Detection was performed at 205 nm. The detection limit of the method was 5 X 10(-6) M and the linear dynamic range was over 500. No sample clean-up procedure was necessary other than deproteinization of the plasma. The method was applied to the measurement of plasma drug levels in 3 patients, part of a clinical trial testing the effectiveness of thioproline as an anti-cancer agent.

Antineoplastic Agents↗
PubMed1981

Inhibition of cell growth by N-(phosphonacetyl)-L-aspartate in human and murine cells in vitro.

Two murine cell lines, L1210 leukemia (T-cell) and B16 melanoma, and 3 human cell lines, CCRF-CEM leukemia (T-cell), NC37 lymphoblasts (B-cell) and IPC-48 melanoma were compared with respect to sensitivity to N-(phosphonacetyl)-L-aspartate (PALA), growth rate and aspartate transcarbamylase activity. No correlation between drug sensitivity and growth rate was found. The melanoma cell lines were more sensitive to PALA than were the lymphocytic cell lines. The 2 T-cell leukemia lines had similar sensitivities to PALA while the B-lymphoblasts were more resistant at 10(-3) M PALA and less resistant at 10(-4) M PALA than were L1210 and CCRF-CEM cells. Aspartate transcarbamylase activity was similar among the 2 melanoma cell lines and among the 3 lymphocytic cell lines and was 2-fold higher in the latter.

Animals↗
PubMed1981

Methotrexate cytotoxicity: studies on its reversal by folates and nucleosides.

The methotrexate (MTX) metabolite, 7-hydroxymethotrexate, which is potentially capable of influencing MTX rescue by affecting both MTX and reduced folate transport at the cell membrane, has been estimated in the plasma of patients receiving moderate doses (240 mg/m2) of MTX. Forty-eight hours after MTX dosage the level of 7-hydroxymethotrexate exceeded that of MTX by ten to one. Studies of the utilization of thymidine and inosine by MTX-treated L1210 cells in culture suggest that these cells may be able to utilize these substrates when their extracellular concentration is less than 1 microM. The incorporation of 14C hypoxanthine into the nucleotide pools and the nucleic acids of L1210 cells increases following exposure to MTX. This observation is compatible with the known increased availability of phosphoribosyl pyrophosphate in these cells following MTX treatment. These observations show ways in which naturally occurring nucleosides as well as metabolites of MTX itself may modulate the toxicity of the drug. Such observations may be relevant to the design of treatment and rescue protocols.

Animals↗