Low anion gap resulting from unexplained exposure to bromide in a patient with renal amyloidosis.

A patient with nephrotic syndrome secondary to renal amyloidosis was consistently observed to have serum anion gap levels as low as -1 mEq/L and averaging approximately 2 mEq/L. Neither multiple myeloma nor extreme hypertriglyceridemia was present, and the patient's serum albumin concentrations were not low enough to depress the anion gap to this degree. An increased serum bromide level (below the range expected to produce clinical toxicity) was the apparent cause of the low anion gap. The patient's parents, who live in the same apartment, also manifested low anion gaps and inexplicably elevated serum bromide levels. Despite detailed investigation, no environmental or pharmacologic source of bromide was uncovered. Although the source of the bromide in the present instance remains elusive, this report illustrates the necessity to measure serum bromide when a low anion gap cannot be explained by other factors, even when there is no history to suggest bromide exposure.

Laboratory verification

Laboratory analysis is needed for verification of suspected pesticide poisoning. Analytical methods for an extensive number of pesticides and their metabolities have been developed (AU)

Radiation, pool size and incorporation studies in mice with 5-chloro-2'-deoxycytidine.

Bolus doses of 5-chlorodeoxycytidine (CldC) administered with modulators of pyrimidine metabolism, followed by X-irradiation, resulted in a 2-fold dose increase effect against RIF-1 tumors in C3H mice. Pool size studies of the fate of [14C]-CldC in BDF1 mice bearing Sarcoma-180 tumors, which demonstrated the rapid formation of 5-chlorodeoxycytidylate (CldCMP), and incorporation of CldC as such in RIF-1 tumor DNA, indicate that CldC is a substrate for deoxycytidine kinase, as our past Km studies have shown. Our data indicate that 5-chlorodeoxyuridine triphosphate (CldUTP) accumulates from both the cytidine deaminase-thymidine kinase pathway, as well as from the deoxycytidine kinase-dCMP deaminase pathway, in tumor tissue. As shown in a previous study, tetrahydrouridine (H4U), a potent inhibitor of cytidine deaminase, can effectively inhibit the enzyme in the normal tissues of BDF1 mice. When H4U was administered with the modulators N-(phosphonacetyl)-L-aspartic acid (PALA) and 5-fluorodeoxycytidine (FdC), the levels of CldC-derived RNA and DNA directed metabolites increased in tumor and decreased in normal tissues compared to when CldC was administered alone. These modulators inhibit the de novo pathway of thymidine biosynthesis, lowering thymidine triphosphate (TTP) levels, which compete with CldUTP for incorporation into DNA. 5-Benzylacyclouridine (BAU), an inhibitor of uridine phosphorylase, was also utilized. DNA incorporation studies using C3H mice bearing RIF-1 tumors showed that the extent of incorporation of 5-chlorodeoxyuridine (CldU) into DNA correlates with the levels of cytidine and dCMP deaminases; this is encouraging in view of their high activity in many human malignancies and the low activities in normal tissues, including those undergoing active replication. Up to 3.9% replacement of thymidine by CldU took place in RIF-1 tumors, whereas incorporation into bone marrow was below our limit of detection. CldC did not result in photosensitization under conditions in cell culture in which radiosensitization to X rays was obtained. Thus, the combination of CldC with modulators of its metabolism has potential as a modality of selective radiosensitization for ultimate clinical use in a wider range of tumors than those of the brain.

Carbamazepine metabolism in humans: effect of concurrent anticonvulsant therapy.

Free and total carbamazepine (CBZ) and carbamazepine-epoxide (CBZ-EP) plasma levels were obtained on 113 patients with epilepsy (18-61 years old) controlled on either monotherapy or coadministration with either phenobarbital (PB), phenytoin (PHT), valproic acid (VPA), or all three. A subset of patients were administered tetradeuterium labeled CBZ to evaluate the effects of autoinduction and coadministration of VPA on the kinetics of CBZ and its metabolite CBZ-EP. Polytherapy had variable effect on free and total CBZ plasma levels compared to monotherapy. Coadministered PHT (co-PHT), or all three anticonvulsants together (PHT, PB, and VPA: co-AEDs) decreased free and total CBZ plasma levels. No change was noted for coadministered VPA (co-VPA). Compared to monotherapy the free and total CBZ-EP levels increased with co-VPA, less with coadministered PB (co-PB), and no change with co-PHT or co-AEDs. Protein binding of CBZ and CBZ-EP was not affected by any antiepileptic drugs studied. The free and total CBZ-EP/CBZ ratio was tripled with co-VPA or co-AED's, and doubled with co-PHT or co-PB. Isotope labeling did not demonstrate any differences in half-life (t1/2), plasma clearance (Cl), or volume of distribution (Vd). Compared to naive controls, monotherapy and co-VPA decreased CBZ t1/2 by 50%, and more than doubled the CBZ Cl without a significant change in the Vd. Autoinduction is one explanation for these changes with chronic CBZ therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Tumor-selective metabolism of 5-fluoro-2'-deoxycytidine coadministered with tetrahydrouridine compared to 5-fluorouracil in mice bearing Lewis lung carcinoma.

The metabolic products formed and incorporated into the nucleic acids (RNA and DNA) of mice bearing Lewis lung carcinoma (LLC) following optimal doses of 5-fluorouracil (FUra), 5-fluoro-2'-deoxyuridine (FdUrd), and 5-fluoro-2'-deoxycytidine (FdCyd) coadministered with tetrahydrouridine (H4Urd), a potent inhibitor of cytidine deaminase, were examined. Treatment with FdCyd plus H4Urd resulted in a tumor-selective incorporation and formation of antimetabolites compared to either FUra or FdUrd treatments. Between 45- and greater than 5400-fold higher levels of the potent thymidylate synthetase inhibitor, 5-fluoro-2'-deoxyuridylate (FdUMP), were formed in tumor than in any of the normal tissues analyzed. RNA-level antimetabolites (FUra, 5-fluorouridine, and 5-fluorouridylate) were also between 3 and greater than 990-fold higher in tumor compared to normal tissue following FdCyd plus H4Urd administration. DNA-level antimetabolites (FdCyd, 5-fluorodeoxycytidylate, FdUrd, and FdUMP) were from 2- to 6-fold higher in tumor compared to normal tissue. FUra and FdUrd treatments resulted in between 3 and greater than 1300-fold higher RNA-level antimetabolites and from 4 to greater than 1020-fold higher FdUMP pools in normal tissues than FdCyd plus H4Urd treatment. DNA-level antimetabolites were also from 4- to 32-fold higher in normal tissues following optimal doses of FUra or FdUrd. In tumor tissue, optimal doses of FUra or FdUrd resulted in lower (a) FdUMP levels (5- to 2-fold), (b) RNA-level antimetabolites (6- to 3-fold), and (c) DNA-level antimetabolites (10- to 4-fold) compared to an optimal dosage of FdCyd plus H4Urd. In serum, the administration of H4Urd resulted in the protection of FdCyd from systemic catabolism, unlike that found with FUra or FdUrd. Substantial levels of FdUMP, FUrd, and FUMP were noted in serum following FUra or FdUrd treatment. The formation of di- and triphosphate antimetabolite pools and the incorporation of antimetabolites into the RNA and DNA of normal and tumor tissues demonstrated trends similar to those mentioned above with nucleoside, mononucleotide, and free base pools. H4Urd treatment of 25 mg/kg did not affect the elevated levels of deoxycytidine kinase or deoxycytidylate deaminase in LLC tumor tissue or the low levels found in normal tissue. A critical feature of this chemotherapeutic strategy using FdCyd plus H4Urd was that the elevated level of cytidine deaminase in LLC tumor tissue was inhibited less than 10% by the administration of 25 mg/kg H4Urd, whereas deoxycytidine deaminase activities in normal tissues (including bone marrow and intestine) were inhibited greater than 93%.(ABSTRACT TRUNCATED AT 400 WORDS)

Protective, tumor-selective dual pathway activation of 5-fluoro-2'-deoxycytidine provided by tetrahydrouridine in mice bearing mammary adenocarcinoma-755.

Treatment of C57BL X DBA/2 F (hereafter called BD2F) mice bearing ascitic mammary adenocarcinoma-755 (ADC-755) with [3H]-5-fluoro-2'-deoxycytidine ([3H]FdCyd) plus tetrahydrouridine (H4Urd) resulted in antimetabolite pool sizes indicative of a tumor-selective, dual pathway metabolism of FdCyd via both cytidine deaminase and deoxycytidine kinase. In contrast to the high levels of all RNA- and DNA-level antimetabolites (as assayed by high performance liquid chromatography) derived from FdCyd found in tumor tissue, normal tissues (bone marrow, intestine, liver, and spleen) and serum metabolized FdCyd to only a small extent following FdCyd plus H4Urd treatment. RNA-level antimetabolite pools and 5-fluoro-2'-deoxyuridine (FdUrd) were generally 100-fold lower in normal than in tumor tissue, and 5-fluoro-2'-deoxyuridylate was 10- to 15-fold lower in normal than in tumor tissue. The use of [3H]FdUrd, on the other hand, resulted in the formation of higher levels (10- to 40-fold) of DNA- and RNA-level antimetabolites in normal tissue and lower levels (1/8) of 5-fluoro-2'-deoxyuridylate in tumor tissue. Both [3H]FdCyd plus H4Urd and [3H]FdUrd were utilized at their optimal drug doses. FdUrd- and FdCyd-derived metabolic products incorporated into the RNA and DNA of normal and tumor tissue of BD2F mice bearing ADC-755 were also examined. The drug combination [3H]FdCyd plus H4Urd resulted in the selective incorporation of antimetabolites into tumor RNA and DNA; only a very small extent of antimetabolites incorporated into normal tissue RNA and DNA. FdCyd was incorporated 5- to 10-fold greater in tumor than intestine, liver, or spleen following FdCyd plus H4Urd administration. FdCyd incorporation was 190-fold greater in tumor than in bone marrow. Mice bearing ADC-755 treated with [3H]-FdUrd resulted in only marginal selectivity in terms of antimetabolite incorporation in tumor tissue. Deoxycytidylate and cytidine deaminase enzyme assays have confirmed that H4Urd administration effectively inhibited normal cytidine deaminase activities, while only weakly inhibiting the elevated levels found in tumor tissue. Thymidine kinase, deoxycytidine kinase, deoxycytidylate deaminase, and cytidine deaminase have been shown previously to be significantly elevated in the mouse tumor model used; these enzymatic elevations are also characteristic of many human tumors. Treatment with FdCyd plus H4Urd resulted in 17 of 30 cures against ADC-755 compared to 4 of 20 and 0 of 20 for 5-fluorouracil and 5-fluoro-2'-deoxyuridine treatments, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of 5-fluoro-2'-deoxycytidine and 5-trifluoromethyl-2'-deoxycytidine and their related antimetabolites by high-performance liquid chromatography.

An isocratic, ion-paired, reversed-phase high-performance liquid chromatography technique for the quantitative determination of 5-fluoro-2'-deoxycytidine (FdCyd) and 5-trifluoromethyl-2'-deoxycytidine (F3methyldCyd) and their related antimetabolites is described. Extraction and purification of these compounds from DNA, RNA, and free pools is reviewed diagrammatically. Total analysis time including quantitation of DNA and RNA primary constituents is 45 min. Average combined recoveries for prodrugs and antimetabolites is above 90% with standard deviations of 0.07 and 0.58 and average precisions of 5.51 and 8.30% for FdCyd and F3methyldCyd, respectively. Average coefficients of variation were 3.8 +/- 0.5% for FdCyd and 7.7 +/- 1.0% for F3methyldCyd. Limits of detection were approximately 1 pmol for unlabelled prodrugs and antimetabolites. FdCyd, when generally tritiated with a specific activity of 18 Ci/mmol, was detected in the 5 X 10(-15)-20 X 10(-15) mol (fmol) range depending on sample condition.

Metabolic channeling of 5-fluoro-2'-deoxycytidine utilizing inhibitors of its deamination in cell culture.

The metabolism of 5-fluoro-2'-deoxycytidine (FdC) with and without tetrahydrouridine (H4U) or 2'-deoxytetrahydrouridine (dH4U) was examined in log phase HEp-2 cells using HPLC and TLC methods which quantified: the incorporation of FdC-related antimetabolites into RNA and DNA and pool size levels of FdC-related antimetabolites. [3H]-FdC administered to log phase HEp-2 cells at a concentration of 0.01 microM for 24 hr resulted in the incorporation of 5.22 X 10(-8) mol of FdC/mol of DNA phosphate, a 0.021% substitution of FdC for dC. Coadministration of 1.0 mM H4U or dH4U resulted in 2- and 25-fold increases in the incorporation of FdC, respectively. No detectable incorporation of 5-fluoro-2'-deoxyuridine (FdU) into HEp-2 DNA resulted (detection limit, approximately 5 fmol). In contrast, treatment of HEp-2 cells with 0.1 microM FdU resulted in the incorporation of 1.83 X 10(-9) mol of FdU (74.7 fmol detected)/mol of DNA phosphate. A linear incorporation of FdC into the DNA of HEp-2 cells was found with increasing concentrations of FdC and 1.0 mM dH4U . 0.1 microM FdC resulted in the incorporation of 2.39 X 10(-6) mol of FUMP/mol of cytoplasmic RNA phosphate and 2.23 X 10(-5) mol of FUMP/mol of nuclear RNA phosphate. Similarly, HEp-2 cells treated with 0.1 microM FdU resulted in the incorporation of 1.10 X 10(-5) mol of FUMP/mol of nuclear RNA phosphate and 9.44 X 10(-7) mol of FUMP/mol of cytoplasmic RNA phosphate. In contrast, no detectable FUMP incorporation into either nuclear or cytoplasmic RNAs of HEp-2 cells resulted when H4U or dH4U was coadministered with 0.1 microM FdC. Pool size analyses of log phase HEp-2 cells following a 30-min exposure to FdU or FdC with and without H4U or dH4U were also performed; 0.1 microM FdC treatment resulted in the formation of 169 fmol of FUMP/1.0 X 10(6) viable HEp-2 cells. Treatment with 0.1 microM FdU produced 253 fmol of FUMP/1.0 X 10(6) viable HEp-2 cells. In contrast, no detectable FUMP pools were formed when H4U or dH4U was coadministered with 0.1 microM FdC (detection limit, approximately 5 fmol). Pool levels of FdUMP, the inhibitor of thymidylate synthetase, were also assayed; 36.9 fmol of FdUMP/1.0 X 10(6) viable HEp-2 cells were detected upon administration of 0.1 microM FdC.(ABSTRACT TRUNCATED AT 400 WORDS)

Marked radiosensitization of cells in culture to X ray by 5-chlorodeoxycytidine coadministered with tetrahydrouridine, and inhibitors of pyrimidine biosynthesis.

Our approach to overcome the problem of rapid catabolism and general toxicity encountered with 5-halogenated analogues of deoxyuridine (5-bromo, chloro or iododeoxyuridine), which has limited their use as tumor radiosensitizers, is to utilize 5-chlorodeoxycytidine (CldC) with tetrahydrouridine (H4U). We propose that CldC, coadministered with H4U, is metabolized in the following manner: CldC----CldCMP----CldUMP---- ----CldUTP----DNA. All the enzymes of this pathway are elevated in many human malignant tumors and in HEp-2 cells. In X irradiation studies with HEp-2 cells, limited to 1 or 2 radiation doses, we have obtained 3.0 to 3.8 apparent dose enhancement ratios (these represent upper limits) when cells are preincubated with inhibitors of pyrimidine biosynthesis: N-(Phosphonacetyl)-L-aspartate (PALA) and 5-fluorodeoxyuridine (FdU) or 5-fluorodeoxycytidine (FdC) + H4U. Optimum conditions for radiosensitization are: PALA (0.1 mg/ml) 18-20 hr prior to FdU (0.1 microM) or FdC (0.02 microM) + H4U (0.1 mM) followed 6 hr later by CldC (0.1-0.2 mM) + H4U (0.1 mM) for 56-68 hr. Viabilities of 10 +/- 4% to 15 +/- 1% (+/- S.E.) were obtained for drug-treated unirradiated cells. Enzymatic studies indicate that this toxicity may be tumor selective. CldC + H4U alone (at these concentrations) results in 20% substitution of CldU for thymidine in DNA (determined by HPLC analysis). Preliminary toxicity studies indicate that mice will tolerate treatment protocols involving a single dose of PALA (200 mg/kg) followed by a dose of FdU (50 mg/kg) and 3 cycles of CldC (500 mg/kg) + H4U (100 mg/kg) at 10 hour intervals, with marginal weight loss (4%). In this approach we seek to obtain preferential conversion of CldC to CldUTP at the tumor site by taking advantage of quantitative differences in enzyme levels between tumors and normal tissues.

Membrane-associated carbonic anhydrase purified from bovine lung.

We found carbonic anhydrase activity associated with particulate fractions of homogenates of rat, rabbit, human, and bovine lungs. These membrane-associated carbonic anhydrases were remarkably stable in solutions containing sodium dodecyl sulfate (SDS). The bovine enzyme was dissolved with SDS and purified by affinity chromatography and gel filtration. The purified enzyme contains glucosamine, galactose, and sialic acid; it is at least 20% carbohydrate. The apparent molecular weight by SDS-polyacrylamide gel electrophoresis (52,000) may be higher than the actual molecular weight due to the presence of carbohydrate. The enzyme contains cystine, an amino acid that is absent in bovine erythrocyte carbonic anhydrase. Dithiothreitol greatly accelerated the rate of inactivation of the membrane-associated enzyme in SDS, so disulfide bonds appear to stabilize this enzyme. The specific CO2-hydrating activity was about half that of the erythrocyte enzyme. Acetazolamide inhibits the membrane-associated enzyme (Ki = 10 nM) nearly as well as the erythrocyte enzyme (Ki = 3 nM). Antibody to bovine erythrocyte carbonic anhydrase did not inhibit the membrane-associated enzyme. Other investigators have accumulated a good deal of evidence for carbonic anhydrase on the luminal surface of pulmonary capillaries. The enzyme described here appears to be a new isozyme whose properties are consistent with such a localization.

High performance liquid chromatographic determination of cyanuric acid in human urine and pool water.

A reverse phase high performance liquid chromatographic (HPLC) assay for the quantitative determination of cyanuric acid (CA) in urine and water is described. For purification, samples are passed through a pre-activated reverse phase C18 column. The effluent is dried by lyophilization, and the residue is reconstituted in hexane-washed water and then passed through a prewashed Dowex-1 column. The effluent is again dried by lyophilization, and the dry residue is extracted with hot dioxane. The solution is cooled to ambient temperature and centrifuged. The supernatant liquid is removed, dried under a nitrogen steam, and dissolved in water for final extraction by reverse phase chromatography. This effluent is dried, dissolved in the sodium phosphate monohydrate in methanol (pH 7.0) mobile phase, and injected into a pre-equilibrated chromatographic system. An external standard is used for quantification by peak height comparison. A sample of HPLC column effluent is collected, dried, dissolved in methanol, and used for mass spectrometric confirmation by a solid probe insert procedure. Average combined recovery determined at 1.0, 5.0 and 10.0 micrograms CA/mL is 103 +/- 3% with an average coefficient of variation of 8.6%. Standard deviations for the 3 concentration levels are 0.04, 0.58, and 0.76, respectively, with average precisions of 4.28, 10.92, and 7.61%. The limits of detection are approximately 0.05 micrograms/mL for urine and 0.1 micrograms/mL for swimming pool water. Recorder response to CA is linear over the concentration range 1-10 microgram/mL.