Biomedical subjects

P C Smith

Publications and source records attributed to P C Smith.

At least 19 recordsLinked to original sources

PubMed1996

Direct analysis of salicylic acid, salicyl acyl glucuronide, salicyluric acid and gentisic acid in human plasma and urine by high-performance liquid chromatography.

A method for the simultaneous direct determination of salicylate (SA), its labile, reactive metabolite, salicyl acyl glucuronide (SAG), and two other major metabolites, salicyluric acid and gentisic acid in plasma and urine is described. Isocratic reversed-phase high performance liquid chromatography (HPLC) employed a 15-cm C18 column using methanol-acetonitrile-25 mM acetic acid as the mobile phase, resulting in HPLC analysis time of less than 20 min. Ultraviolet detection at 310 nm permitted analysis of SAG in plasma, but did not provide sensitivity for measurement of salicyl phenol glucuronide. Plasma or urine samples are stabilized immediately upon collection by adjustment of pH to 3-4 to prevent degradation of the labile acyl glucuronide metabolite. Plasma is then deproteinated with acetonitrile, dried and reconstituted for injection, whereas urine samples are simply diluted prior to injection on HPLC. m-Hydroxybenzoic acid served as the internal standard. Recoveries from plasma were greater than 85% for all four compounds over a range of 0.2-20 micrograms/ml and linearity was observed from 0.1-200 micrograms/ml and 5-2000 micrograms/ml for SA in plasma and urine, respectively. The method was validated to 0.2 microgram/ml, thus allowing accurate measurement of SA, and three major metabolites in plasma and urine of subjects and small animals administered salicylates. The method is unique by allowing quantitation of reactive SAG in plasma at levels well below 1% that of the parent compound, SA, as is observed in patients administered salicylates.

Chromatography, High Pressure Liquid↗

PubMed1996

Predictors of survival in human immunodeficiency virus type 1-seropositive intravenous drug users.

In an ongoing prospective study of street-recruited intravenous drug users (IDUs) in Miami, Fla., 116 human immunodeficiency virus type 1 (HIV-1)-infected IDUs were monitored for up to 7 years. This provided an opportunity to evaluate baseline immunological parameters as potential predictors of survival among HIV-1-infected IDUs. As expected, HIV-1-infected IDUs who had an advanced stage of the disease (Centers for Disease Control and Prevention classification III or IV); p24 antigenemia; human T-cell leukemia virus type 1/2 seropositivity; low CD4 counts (< or = 200); low hemoglobin (< or = 14), high serum immunoglobulin A (IgA) (> 500 mg/dl), or high serum IgG (> or = 3,500 mg/dl) levels; or low proliferative responses to pokeweed mitogen (< or = 1,500 cpm) and to phytohemagglutinin (< or = 80,000 cpm) at baseline had worse survival rates. Results from multivariate Cox's models of survival showed that the baseline serum IgG level, serum IgA level, and CD4 count independently predict survival in HIV-1-infected IDUs. Cross-validation procedures verified the above-mentioned findings. These findings support the routine consideration of serum immunoglobulin levels in addition to CD4 count, especially in early evaluation of disease stage, as these evaluations may modify application of prophylaxis and treatment for HIV-1-infected IDUs. We recommend consideration of use of serum IgG and IgA as immunological markers for long-range prediction of survival in HIV-1-infected IDUs. These determinations are less onerous and more appropriate for use in field studies and financially less favored settings.

Adult↗

PubMed1996

A two-site monoclonal antibody immunoradiometric assay for human follistatin: secretion by a human ovarian teratocarcinoma-derived cell line (PA-1).

The follistatin/activin/inhibin system increasingly appears to have important growth and differentiating effects in a variety of cell types, including cancer. We have developed a two-site immunoradiometric assay for measurement of human follistatin using two monoclonal antibodies against recombinant human follistatin. This cloned protein donor assay is sensitive (0.5 ng/mL), specific for free human follistatin, and precise (<5% within assay coefficient of variation). Using this assay, native human follistatin could be measured in human pituitary extracts, follicular fluid, and granulosa-luteal cell-conditioned medium. To identify and characterize human follistatin secreted by ovarian cancer cells, we screened five human ovarian carcinoma cell lines currently available from the American Type Culture Collection (Rockville, MD). One of these, a cell line derived from a teratocarcinoma (designated PA-1, American Type Culture Collection, CRL1572), secreted large (3 microg/10(6) cells per 24 h) quantities of immunoreactive follistatin constituitively. Increasing volumes of conditioned medium from these cultured cells generated response curves parallel to those of recombinant human follistatin 288 reference protein, human follicular fluid, or culture medium from human granulosa-luteal cells. Secretion of follistatin by PA-1 cells was time and cell-number dependent with 297.9 +/- 15.2, 654 +/- 29.8, and 940 +/- 49.1 ng follistatin secreted over 24 h by 1 x 10(5), 2 x 10(5), and 3 x 10(5) cells, respectively. Western and ligand blot analysis revealed that the immunoreactive follistatin secreted by PA-1 cells and isolated by sulfate-cellufine chromatography was identical to the molecular weight variants (32,000 and 35,000 Mr) of recombinant human follistatin 288. PA-1 cell-conditioned medium suppressed basal secretion of FSH by cultured rat anterior pituitary cells in a dose-dependent fashion. This follistatin bioactivity was completely removed by adsorption with either solid-phase monoclonal antifollistatin or a dextran-sulfate chromatography gel. Because activin suppressed the proliferation of PA-1 cells, secretion of bioactive follistatin may represent an autocrine mechanism opposing activin to maintain the rapid growth rate of PA-1 cells. These observations demonstrate that the ovarian teratocarcinoma cell line, PA-1, secretes considerable amounts of human follistatin that is biologically active, capable of binding human activin, and antigenically similar to recombinant human follistatin 288. The monoclonal antibodies and two-site assay reported herein should be useful in assessing the regulation of follistatin secretion and as a diagnostic tool, especially if follistatin measurements prove to be a marker for some ovarian cancers.

Activins↗

PubMed1996

Homologous in vitro bioassay for follicle-stimulating hormone (FSH) reveals increased FSH biological signal during the mid- to late luteal phase of the human menstrual cycle.

Monitoring of the secretory dynamics of FSH during the human menstrual cycle has demonstrated conflicting results between the amounts of FSH measured by dimer-specific immunoassays and previous heterologous in vitro bioassays. These differences suggest somewhat different models of the steroidal and nonsteroidal regulation of FSH secretion and its control of folliculogenesis in the human. We have developed a homologous in vitro bioassay, using the recombinant human FSH receptor cotransfected into Chinese hamster ovary cells with a cAMP-responsive luciferase reporter gene, that overcomes many of the theoretic shortfalls of previous assays and allows reevaluation of the changes in bioactive FSH across the menstrual cycle. Bioactive FSH levels measured across 12 menstrual cycles in 11 normal women ranged from 4-40 IU/L. FSH bioactivity was constant during the menstrual cycle, with elevations noted only during the mid- to late luteal phase. Bioactive FSH levels were similar to immunoactive FSH levels across the cycle as indicated by a ratio of bioactive to immunoreactive FSH (FSH B/I) of 1.10 +/- 0.04 across the follicular and early luteal phases. However, during the mid- to late luteal phase, the mean FSH B/I rose to 1.65 +/- 0.07, which significantly exceeded that during the rest of the cycle (P < 0.001). This change in FSH B/I occurs at a critical time during folliculogenesis when the next cohort of follicles is being recruited and appears to be secondary to a decrease in immunoreactive FSH unaccompanied by a similar decrease in in vitro bioactivity. There was good agreement between immunoassay and bioassay results on the day of the midcycle gonadotropin surge (FSH B/I = 1.07 +/- 0.14), which was not different from that in the follicular phase (days -17 to -2; FSH B/I = 1.06 +/- 0.05) or the FSH B/I measured in postmenopausal women (0.93 +/- 0.2). These observations using a novel homologous human FSH in vitro bioassay indicate that bioactive FSH levels are not declining during the time of active corpus luteum formation and secretory activity. Thus, there is a previously undetected increased biologic signal during the mid- to late luteal phase, suggesting that the influence of elevated FSH on the cohort of developing follicles (including the subsequent dominant follicle) begins earlier during the luteal-follicular transition than previously predicted by FSH immunoreactivity.

Adult↗

PubMed1996

Influence of renal failure in rats on the disposition of salicyl acyl glucuronide and covalent binding of salicylate to plasma proteins.

Many acyl glucuronides are labile, reactive and form covalent adducts with proteins. In the present experiment, the stability of salicyl acyl glucuronide (SAG), its reactivity with serum albumin in vitro and the influence of renal failure in rats on the disposition of SAG and covalent binding of salicylate (SA) to rat plasma proteins were investigated. In vitro studies showed that SAG was hydrolyzed to SA or undergoes isomerization to positional isomers. The half-life of SAG was 1.3 hr in 0.15 M phosphate buffer at pH 7.4 and 37 degrees C, but the stability of its isomers was much greater with an apparent half-life of 19 hr. Incubation of SAG in solutions of human serum albumin revealed the formation of covalent adducts with the protein, with maximal binding of 2.8% of total SA equivalents added to the solution. For in vivo studies, one group of rats was administered 5 mg/kg of uranyl nitrate i.p. to induce renal failure. After administration of 100 mg/kg of SA i.v., the AUC 0-26 hr of SAG in rats with renal failure was 9 times higher than that observed in control rats. The apparent clearance of SA decreased from 64 +/- 21 ml/hr in control rats 28 +/- 8.7 ml/hr in rats with renal failure. The level of SA covalent adducts with plasma proteins reached about 0.5 ng/mg of protein in control rats, whereas in rats with renal failure the binding was increased significantly and achieved an average peak concentration of 18 ng/mg of protein when measured 26 hr after dosing. The data indicate that reactive SAG can accumulate in renal failure which then increases covalent addition of SA to proteins. Such binding may have a role in enhancing the potential for toxicity of acidic drugs such as SA in renal disease.

Animals↗

PubMed1995

Disposition and covalent binding of ibuprofen and its acyl glucuronide in the elderly.

Ibuprofen is an over-the-counter nonsteroidal anti-inflammatory drug with a low incidence of severe adverse reactions. It is metabolized by oxidation to carboxyibuprofen and hydroxyibuprofen and by conjugation to an acyl glucuronide. In vitro studies have indicated that ibuprofen glucuronide is labile and reactive, forming covalent adducts with proteins. To verify the formation of ibuprofen-protein adducts in vivo, the pharmacokinetics of ibuprofen glucuronide and its covalent binding to plasma proteins were studied in five elderly patients who received long-term administration of oral doses of ibuprofen. Plasma levels of ibuprofen glucuronide were low relative to those of ibuprofen; the ratio of area under the plasma concentration versus time curve for the glucuronide relative to the parent drug was only 4%. Covalent binding of ibuprofen to plasma protein was observed in all patients, correlating well with the area under the plasma concentration versus time curve of ibuprofen glucuronide (r = 0.966). Compared with reports for other nonsteroidal anti-inflammatory drugs that form acyl glucuronides, plasma levels of ibuprofen-protein adduct are low during long-term administration. The observed lower reactivity in vivo is probably attributable to the greater stability of ibuprofen glucuronide relative to other acyl glucuronides.

Administration, Oral↗

PubMed1995

Comparative tissue distribution and elimination of amphotericin B colloidal dispersion (Amphocil) and Fungizone after repeated dosing in rats.

The pharmacokinetic profiles of amphotericin B (AmB) after administration of Amphocil, an AmB/cholesteryl sulfate colloidal dispersion (ABCD) and the micellar AmB/deoxycholate (Fungizone) were compared after repeated dosing in rats. After administration of ABCD and Fungizone at an equal AmB dose (1 mg/kg), AmB concentrations in plasma and most tissues were lower for the ABCD dose, especially in the kidneys where reduced drug concentration correlated with reduced nephrotoxicity. In contrast, AmB concentrations in the liver were substantially higher when ABCD was administered; however, without an accompanying increase in hepatotoxicity. Daily administration of ABCD for 14 days did not lead to AmB accumulation in plasma; while a slight accumulation was observed after multiple administration of Fungizone. AmB was eliminated more slowly from the plasma and various tissues and urinary and fecal recoveries of AmB were reduced after ABCD administration. These results suggest that ABCD may be stored in tissues in a form that is less toxic and is eliminated from the systemic circulation by a different mechanism than the free and protein-bound AmB in plasma. AmB accumulation in the spleen was observed when higher, doses of ABCD (5 mg/kg) were administered, which could be due to saturation of hepatic uptake of AmB. Comparison of spleen concentrations of AmB between ABCD and Fungizone at 5 mg/kg AmB doses was not possible because of Fungizone's toxicity in rats. In all other organs, AmB concentrations reached or approached a steady state within two weeks of dosing with ABCD. Urinary and fecal clearences of AmB were not different between ABCD and Fungizone administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Amphotericin B↗

PubMed1995

Covalent binding of suprofen to renal tissue of rat correlates with excretion of its acyl glucuronide.

1. Dosing rat with suprofen produces suprofen equivalents that are covalently bound to plasma and tissue proteins in vivo. 2. Suprofen acyl glucuronide is reactive in vitro, resulting in suprofen equivalents covalently bound to proteins of plasma and tissues in a time-dependent manner. 3. Bile duct ligation of rat increases exposure to suprofen acyl glucuronide in vivo, which leads to enhanced covalent binding of suprofen equivalents to plasma proteins and to kidney tissue. 4. Covalent binding of suprofen equivalents to kidney tissue correlates with excretion of suprofen and suprofen glucuronide by the kidney.

Animals↗

PubMed1995

Disposition and reactivity of ibuprofen and ibufenac acyl glucuronides in vivo in the rhesus monkey and in vitro with human serum albumin.

The disposition of ibuprofen and ibufenac, an analog of ibuprofen with a history of severe adverse reactions, was investigated in Rhesus monkeys after oral administration. Plasma concentrations of the parent drugs and their glucuronides were measured by a direct HPLC method. Ibuprofen and ibufenac were rapidly absorbed and metabolized to their acyl glucuronides. The pharmacokinetic parameters of ibuprofen and ibufenac exhibited notable interanimal variability. Ibufenac tended to have a higher area under the plasma concentration vs. time curve (AUC), and its apparent clearance was lower. The plasma levels of acyl glucuronides were lower than parent drugs; the ratio of AUC in plasma for glucuronide/parent drug was 22.8% and 10.5% for ibuprofen and ibufenac, respectively. The degradation of ibufenac glucuronide in vitro was faster than ibuprofen glucuronide in aqueous buffer, human serum albumin, and human plasma solutions. Covalent binding of parent drug to protein via the acyl glucuronides was observed both in vitro and in vivo. The maximum protein adduct formed in vivo with ibufenac was 60% higher than found for ibuprofen, although exposure in plasma to its reactive acyl glucuronide, as measured by AUC, was lower. These data indicate that ibufenac glucuronide is a more reactive metabolite than ibuprofen glucuronide in vitro and in vivo.

Animals↗

PubMed1995

Isolation and characterization of Trichinella pseudospiralis Garkavi, 1972 from a black vulture (Coragyps atratus).

A nematode from the genus Trichinella was observed in histological sections of breast and tracheal muscles from a black vulture Coragyps atratus from Alabama. Larvae obtained from breast muscle tissue that had been refrigerated for 8 days were infectious for laboratory mice. No nurse cell was observed around larvae in the black vulture or in experimentally infected mice examined 7 or 9 wk postinoculation. The identity of the parasite as Trichinella pseudospiralis was confirmed by DNA hybridization using the species-specific probe, pTsp 5.32. Infectivity trials showed that this isolate was also infective for pigs and chickens. This is the first report of isolation and transmission of T. pseudospiralis from an animal from North America.

Alabama↗

PubMed1994

Femtomole detection of amino acids and dipeptides by gas chromatography-negative-ion chemical ionization mass spectrometry following alkylation with pentafluorobenzyl bromide.

Amino acids and di- and tripeptides were derivatized by extractive alkylation using pentafluorobenzyl bromide (PFBBr) followed by reaction with heptafluorobutyric anhydride (HFBA) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). Good chromatographic separation and the formation of intense diagnostic ions were observed for the derivative when examined using gas chromatography-negative-ion chemical ionization mass spectrometry (GC-NICI-MS). Of the 20 amino acids investigated, only Arg and Glu could not be detected by this method. Also, dipeptides which included neutral amino acid residues were derivatized with more success than those containing either acidic or basic residues. Each of the amino acids or dipeptides formed one major derivative with the exception of Asn which formed two derivatives with either one or two HFB groups. This derivatization method was optimized with respect to the reaction temperature, reaction time, and choice of derivatizing reagents. Recoveries of derivatized [3H]-labeled Phe, Lys, and Thr were 76, 55, and 34%, respectively. Linearity was observed from 10 to 2000 pg of Ala per vial; selected-ion monitoring provided a detection limit of less than 150 fg with a signal-to-noise (S/N) ratio of 80 to 1. This method has proven to work well with urine samples and shows great promise for the detection of small peptides at low levels.

Acylation↗

PubMed1994

Estradiol and progesterone production by cultured granulosa cells cryopreserved from in vitro fertilization patients.

Gonadotropin-stimulated steroidogenesis was studied in cultured human granulosa-lutein cells obtained from patients undergoing procedures for in vitro fertilization. The impact of cryopreservation on cell function in vitro was studied. Granulosa cells obtained from in vitro fertilization patients were cultured in serum-supplemented medium or cryopreserved at -135 degrees C for 2-22 months. Fresh (unfrozen) cells (10(5) produced estradiol at a rate of 1320 pmol/l (over 72 h) and progesterone at about 2500 nmol/l. Estradiol production by either fresh or cryopreserved granulosa cells in culture was unaffected by physiological concentrations of follicle-stimulating hormone (7 IU/l). Adding testosterone (10(-7) mol/l) to the medium increased estradiol secretion approximately sixfold. In contrast, progesterone production was not affected by follicle-stimulating hormone or testosterone. No significant differences were observed in cultures of cryopreserved granulosa cells compared to cultures of unfrozen cells with respect to estradiol secretion, the effects of follicle-stimulating hormone or testosterone on estradiol secretion, or progesterone production. Progesterone production by fresh and cryopreserved cells was stimulated by human chorionic gonadotropin. These data indicate that cryopreservation offers the potential to facilitate prospective studies utilizing large numbers of human granulosa-lutein cells in culture.

Aromatase↗

PubMed1993

Direct determination of ibuprofen and ibuprofen acyl glucuronide in plasma by high-performance liquid chromatography using solid-phase extraction.

A method for the simultaneous determination of ibuprofen and its labile, reactive metabolite, ibuprofen acyl glucuronide, in plasma is described. Reversed-phase high-performance liquid chromatography (HPLC) employed a C18 column using methanol-10 mM trifluoroacetic acid as the mobile phase with ultraviolet detection at 225 or 214 nm. It is essential that blood is handled rapidly and plasma is acidified upon collection prior to freezing. Plasma samples first are deproteinated with acetonitrile, the supernatant is diluted with phosphate buffer, and ibuprofen, ibuprofen glucuronide, and ibufenac (internal standard) are initially isolated by solid-phase extraction on C18 cartridges. Upon elution, the residue is evaporated, dissolved and injected onto the HPLC system. Recovery is 94 +/- 8 and 70 +/- 9% for ibuprofen glucuronide and ibuprofen, respectively. The measurable concentration range is linear from 0.1 to 10 micrograms/ml for ibuprofen glucuronide and from 0.5 to 100 micrograms/ml for ibuprofen. The method is satisfactory for the analysis of ibuprofen and ibuprofen glucuronide from pharmacokinetic studies in humans. The direct determination of ibuprofen glucuronide allows accurate measurement of this conjugate at low levels relative to the parent compound, ibuprofen, a distinct advantage compared to previously employed indirect methods.

Chromatography, High Pressure Liquid↗

PubMed1993

Internal mammary artery for arterial pressure monitoring after pediatric cardiac operations.

Establishing and maintaining arterial access in pediatric cardiac operations is a frequent and sometimes frustrating problem. We have modified a procedure commonly used in our research laboratory for arterial pressure monitoring and applied it successfully to the pediatric cardiac surgical patient. The internal mammary artery can provide reliable arterial access in the postoperative period.

Blood Pressure Determination↗

PubMed1993

Covalent binding of suprofen acyl glucuronide to albumin in vitro.

1. Suprofen acyl glucuronide, a major metabolite of suprofen in man, is labile, undergoing acyl migration to isomeric conjugates which are not cleaved by beta-glucuronidase. 2. The pH-dependent degradation of diastereomeric suprofen glucuronides in aqueous buffer increases rapidly near physiological pH with an apparent first-order half life of 1.4 h at pH 7.4. 3. Suprofen glucuronide and its isomeric conjugates are reactive with albumin in a pH-dependent manner which corresponds to the stability of the acyl glucuronide. Several per cent of the conjugates added to albumin in solution become covalently bound. 4. The covalent binding of suprofen equivalents to albumin is greatly enhanced by the addition of either cyanide or cyanoborohydride anion, which supports the presence of an imine in the process of binding. Release of isomeric conjugates by treatment of the albumin adduct with dilute acid also supports covalent binding via an imine. 5. The covalent binding of suprofen to proteins through its reactive acyl glucuronide may be of toxicological importance and relevant to the acute renal toxicity observed for suprofen in man.

Albumins↗

PubMed1993

Prevalence of encysted Toxoplasma gondii in raptors from Alabama.

Little is known about the prevalence of encysted Toxoplasma gondii in wild birds. We examined the hearts and breast muscles from 101 raptors for encysted T. gondii. All of the raptors had been submitted for necropsy to the State Veterinary Diagnostic Laboratory, Auburn, Alabama. Tissues were digested in acid-pepsin solution and inoculated into groups of 3-5 laboratory mice. Toxoplasma gondii was isolated from 27 of 101 (26.7%) raptors: 8 of 12 (66.7%) red-shouldered hawks (Buteo lineatus), 13 of 27 (41.1%) red-tailed hawks (Buteo jamaicensis), 1 of 4 (25%) Cooper's hawks (Accipiter cooperi), 1 of 5 (20%) great horned owls (Bubo virginianus), 4 of 15 (26.7%) barred owls (Strix varia), and 1 of 3 (33.3%) kestrels (Falco sparverius). Toxoplasma gondii was not isolated from 3 broad-winged hawks (Buteo platypterus), 3 sharp-shinned hawks (Accipiter striatus), 6 barn owls (Tyto alba), 9 screech owls (Asio otus), a Mississippi kite (Ictinia misisippiensis), 2 golden eagles (Aquila chrysaetos), a bald eagle (Haliaeetus leucocephalus), 4 ospreys (Pandion haliaetus), 4 turkey vultures (Cathartes aura), or 2 black vultures (Coragyps atratus). No significant difference (P > 0.05) in prevalence was detected based on sex using chi-square analysis. Chi-square analysis of the data demonstrated that adult raptors had encysted stages of T. gondii significantly (P < 0.05) more often than did immature raptors.

Age Factors↗

PubMed1993

Development of a DNA probe for identification of bovine herpesvirus 4.

A sensitive and specific DNA probe for detection and identification of bovine herpesvirus 4 (BHV-4) was developed. Cloned fragments from a library of HindIII fragments of the BHV-4 (DN-599) genome were labeled with 32P or digoxigenin and were tested for sensitivity and specificity in detecting viral DNA by dot-blot hybridization. Two probes were identified that detected 10 pg of purified viral DNA, and detected viral DNA in 0.001 micrograms of total DNA extracted from BHV-4-infected cells. Both probes labeled with 32P and 1 labeled with digoxigenin detected viral DNA in samples prepared from cells infected with 2 prototype strains (DN-599 and Movar 33/63) and 4 field isolates of BHV-4. The DNA probes did not hybridize to total DNA prepared from uninfected bovine cells or from cells infected with BHV-1, BHV-2, alcelaphine herpesvirus 1, pseudorabies virus, or equine herpesvirus 1. One probe, labeled with digoxigenin, was tested further by dot-blot hybridization with infected cell lysates that were simply treated with sodium dodecyl sulfate and proteinase K prior to application to the membrane, avoiding extensive DNA purification procedures. This simplified procedure also resulted in specific detection of field isolates of BHV-4 and prototype strains of BHV-4.

Animals↗

PubMed1992

Nonenzymic glycation of albumin by acyl glucuronides in vitro. Comparison of reactions with reducing sugars.

Acyl glucuronides are ubiquitous metabolites formed from acidic xenobiotics and endogenous compounds, such as bilirubin. Previous studies indicated that the covalent binding of acyl glucuronides to proteins occurs via an imine intermediate in a manner analogous to the glycation of proteins via reducing sugars. When glucuronic acid was incubated in solution with albumin, it formed 10 and 4 times more fluorescent, Maillard reaction products with albumin after 25 days than did glucose or fructose, respectively. However, radiolabeled glucuronic acid exhibited less covalent binding to albumin than either glucose or fructose. Circular dichroism measurements indicate that glucuronic acid is about 0.02% open chain form with exposure of the reactive aldehyde, whereas fructose and glucose have 2 and 0.0026% present in solution as the open chain; thus, differences in reactivity of the reducing sugars were not correlated with exposure of the free aldehyde. Methyl glucuronate formed little fluorescent product with albumin, suggesting that the C-6 carboxylate of glucuronic acid may facilitate the reactions after covalent binding that lead to the formation of fluorescent products. When acyl glucuronide metabolites of two previously marketed acidic drugs, zomepirac and suprofen, were incubated with albumin at a concentration of 2.5 mM, more fluorescent product was formed than by 500 mM glucose. Reversible binding of the acyl glucuronides to albumin was 60-90%, but almost zero for the free reducing sugars, which indicates that reversible binding may explain the enhanced reactivity of the acyl glucuronides in forming fluorescent products with albumin. These results indicate that acyl glucuronides are reactive metabolites that may cause significant glycation of proteins with glucuronic acid in vivo.

Animals↗