Concentrations Of Aspirin Research Articles

Comparison of the Pharmacokinetic Profiles of Soluble Aspirin and Solid Paracetamol Tablets in Fed and Fasted Volunteers

SummaryThe aim of this study was to investigate the absorption of popular preparations of two common analgesics – soluble aspirin and solid paracetamol tablets. An open, randomised, crossover study design was used to compare the pharmacokinetic parameters of soluble aspirin and solid paracetamol tablets in 16 healthy, male volunteers from the University of the Witwatersrand, South Africa, in both fed and fasted states. Plasma concentrations of paracetamol, aspirin and salicylic acid were measured. It was found that the rate of absorption was significantly faster for soluble aspirin than for solid paracetamol, regardless of fed or fasting state, considering time to maximum concentration (p < 0.01), time to first quantifiable concentrations (p < 0.05) and absorption rate (p < 0.01). Absorption rate was significantly affected by food for both soluble aspirin (p = 0.028) and for solid paracetamol (p = 0.0003). Time to maximum concentration was not significantly affected by food for soluble aspirin (p = 0.17) but significantly lengthened for solid paracetamol (p = 0.0003). The extent of absorption was affected by food in terms of maximum concentration for both drugs (p = 0.0001), with a reduction of 49% in the fed state for solid paracetamol compared to 18% for soluble aspirin, the difference between the drugs being statistically significant (p = 0.0024). The overall bioavailability of soluble aspirin was unaffected by food and the bioavailability of salicylic acid was increased in the fed state, whereas that of solid paracetamol was lowered in the fed state. Greater inter-individual variation was seen in paracetamol concentrations compared with aspirin or salicylic acid levels. In conclusion, these results show that the absorption of soluble aspirin is largely unaffected by food, whereas, in the same volunteers, the absorption of solid paracetamol tablets is greatly affected. In some volunteers, maximum plasma concentrations of paracetamol following food did not reach levels previously reported to be required for effective analgesia, and this may have implications for pain relief in some individuals. The practice in some individuals of taking aspirin tablets after food to minimise potential gastric disturbance should not affect the level of analgesia.

Omeprazole Does Not Interfere with the Antiplatelet Effect of Low-Dose Aspirin in Man

Background: Experimental studies have shown that omeprazole and other anti-inflammatory agents compromise the therapeutic activity of nonsteroidal anti-inflammatory drugs and aspirin in rats. It is not known whether this effect will occur in humans. Our aim was to determine whether omeprazole affects the antiplatelet effects of low-dose aspirin in humans. Methods: Platelet lumiaggregation, skin bleeding time, plasma levels of aspirin and salicylic acid, and serum gastrin levels were determined in 14 healthy men before and after the ingestion of 125 mg aspirin with or without previous treatment with 20 mg/day of omeprazole for 4 days before testing. Results: Omeprazole increased serum gastrin levels from 64 (median; range, 52-91) pg/ml to 80.5 (median; range, 56-455) pg/ml (P < 0.05) but did not significantly affect the plasma concentration of aspirin or salicylic acid. Aspirin increased skin bleeding time in all subjects, and the increase was similar with and without previous omeprazole treatment. Aspirin inhibited platelet aggregation in response to both collagen and arachidonic acid regardless of omeprazole treatment. Conclusion: A single dose of 20 mg omeprazole daily does not interfere with the biologic activity of 125 mg aspirin on platelets in humans.

Aspirin absorption rates and platelet inhibition times with 325-mg buffered aspirin tablets (chewed or swallowed intact) and with buffered aspirin solution

Large clinical trials such as the second International Study of Infarct Survival routinely gave patients with myocardial infarction a chewed aspirin, yet there are no data to show whether chewing of aspirin is better, or worse, than swallowing a whole tablet. We performed a randomized, placebo-controlled study to determine whether chewing aspirin or administering it in solution accelerates its absorption and antiplatelet activity. On separate days, 12 fasting volunteers ingested 325 mg of buffered aspirin, either by chewing a tablet for 30 seconds before swallowing it with 4 ounces of water, swallowing a whole tablet with 4 ounces of water, or drinking 4 ounces of Alka Seltzer. Frequent blood samples were obtained for serum aspirin, salicylate, and thromboxane B 2 (TxB 2) concentrations. With all formulations of aspirin, serum TxB 2 decreased 50% when the plasma aspirin concentration reached approximately 1,000 ng/ml. A 50% and 90% decrease in serum TxB 2occurred more quickly after chewing a tablet than after a tablet was swallowed whole. For example, the t 50% for serum TxB 2 inhibition was 5.0 ± 0.6 minutes with the chewed tablet versus 12.0 ± 2.3 minutes when the tablet was swallowed (p = 0.01). A 50% decrease in serum TxB 2 occurred 7.6 ± 1.2 minutes after Alka Seltzer solution (p = 0.04 vs chewing a tablet; p = 0.13 vs swallowing a whole tablet). Chewing an aspirin tablet is the most effective way of accelerating absorption of aspirin into the blood and shortening the time required for an antiplatelet effect.

Nonsteroidal Anti-inflammatory Drugs Attenuate Epidermal Growth Factor-Induced Proliferation Independent of Prostaglandin Synthesis Inhibition

Background. The mechanism(s) whereby nonsteroidal anti-inflammatory drugs (NSAIDs) attenuate colorectal tumor growth remains poorly understood. This study determined if NSAIDs decreased epidermal growth factor (EGF)-induced proliferation in human colonic tumor (Caco-2) cells and whether this process involved the inhibition of prostaglandin (PG) synthesis.Methods. Caco-2 cells were serum-starved (48 h) and subsequently treated (48 h) with either serum-free media or EGF (10 ng/ml) ± physiologic and noninjurious (as determined by LDH release) concentrations of aspirin, indomethacin, and ibuprofen. PG synthesis was measured by EIA. Proliferation was quantitated with two assays: cellular protein and nucleic acid content.Results. NSAID treatment did not inhibit growth in cells treated with only serum-free media. Cells exposed to EGF demonstrated a significant increase in PGE2, protein, and nucleic acid. Levels of other eicosanoids (PGI2, TXA2) were minimal both before and after EGF treatment. Despite varying degrees of PGE2 inhibition, each NSAID group equally attenuated EGF-induced protein and nucleic acid synthesis. The correlation between PGE2 levels and protein (R2 = 0.56) or nucleic acid (R2 = 0.54) was poor. Finally, the addition of a physiologically appropriate concentration of exogenous PGE2 failed to reverse NSAID-induced growth inhibition.Conclusion. These data suggest that NSAIDs, independent of PG synthesis inhibition, attenuate EGF-induced proliferation in Caco-2 cells. This may provide one explanation for how NSAIDs limit colonic neoplasia.

Prevention by aspirin and its combination with alpha-difluoromethylornithine of azoxymethane-induced tumors, aberrant crypt foci and prostaglandin E2 levels in rat colon.

The dose-response relationship in male F344 rats was determined for the ability of aspirin administered in the diet to prevent azoxymethane (AOM)-induced colon cancer and aberrant crypt foci (ACF) and to reduce prostaglandin E2 (PGE2) levels. Starting at either 7 or 22 weeks of age, the rats received aspirin. All rats received two doses of AOM (15 mg/kg each on days 7 and 14) and were killed on day 36. The lowest concentrations of aspirin to prevent ACF or reduce PGE2 levels were 600 and 400 mg/kg, respectively. To evaluate the prevention of tumors, rats received either 0 or 400 mg/kg aspirin for a total of 39 weeks with AOM (30 mg/kg) administered 7 days after the start of treatment. Aspirin had no effect on the yield of colon tumors. In a second experiment, rats started to receive 0, 200, 600 or 1800 mg/kg aspirin or 1000 mg/kg alpha-difluoromethylornithine (DFMO) +/- aspirin. Eight and 15 days later, all the rats received 15 mg/kg AOM. Eleven weeks later, animals that were receiving the control diet started to receive 0, 200, 600 or 1800 mg/kg aspirin; 1000 or 3000 mg/kg DFMO; or 1000 mg/kg DFMO + 200 or 600 mg/kg aspirin. The animals were killed 32 weeks later. DFMO effectively reduced the yield of colon tumors when administered starting either before or after AOM while aspirin was much weaker. The combination of aspirin + DFMO administered after AOM was synergistic. Both aspirin and DFMO decreased the Mitotic Index, while apoptosis was increased only by DFMO. Our results demonstrated that aspirin and DFMO could prevent colon cancer when administered after AOM. Furthermore, aspirin reduced ACF, PGE2 levels and mitosis at concentrations that did not prevent cancer. In contrast, the ability to enhance apoptosis did correlate with the prevention of cancer.

Indomethacin increases susceptibility to injury in human gastric cells independent of PG synthesis inhibition.

Indomethacin and other nonsteroidal anti-inflammatory drugs are commonly used to indirectly deduce the possible role of PGs in a process being studied. The objective of this study was to determine if indomethacin, at concentrations comparable to plasma and tissue levels obtained in humans taking therapeutic doses, predisposes human gastric cells to injury through inhibition of PGs or acts through an alternate mechanism. The role of intracellular Ca2+ in this damaging process was also assessed. Indomethacin pretreatment, although by itself nondamaging, was associated with elevated intracellular Ca2+ concentrations and an increased cellular permeability, an effect that was dependent on extracellular Ca2+. Furthermore, indomethacin pretreatment significantly predisposed AGS cells to injury induced by two dissimilar agents (deoxycholate and A-23187), both of which are associated with intracellular Ca2+ accumulation. The addition of exogenous PGs did not reverse the predisposition to injury induced by indomethacin. The observed effects of indomethacin were dependent on concentration and not on ability to inhibit PG synthesis. Similar effects were not observed with equipotent concentrations of ibuprofen or aspirin. Finally, the exacerbation of deoxycholate-induced injury induced by indomethacin was not observed when extracellular Ca2+ was removed. Indomethacin, by disturbing intracellular Ca2+ homeostasis, predisposes human gastric cells to injury through mechanisms independent of PG synthesis. The current study suggests that data resulting from studies employing only indomethacin as a PG synthesis inhibitor should be interpreted with caution.

Butyrylcholinesterase-catalysed hydrolysis of aspirin, a negatively charged ester, and aspirin-related neutral esters

Although aspirin (acetylsalicylic acid) is negatively charged, it is hydrolysed by butyrylcholinesterase (BuChE). Catalytic parameters were determined in 100 mM Tris buffer, pH 7.4, in the presence and absence of metal cations. The presence of Ca 2+ or Mg 2+ (<100 mM) in buffer did not change the K m, but accelerated the rate of hydrolysis of aspirin by wild-type or D70G mutant BuChE by 5-fold. Turnover numbers were of the order of 5000–12 000 min −1 for the wild-type enzyme and the D70G and D70K enzymes in 100 mM Tris, pH 7.4, containing 50 mM CaCl 2 at 25°C; K m values were 6 mM for wild-type, 16 mM for D70G and 38 mM for D70K. People with ‘atypical’ BuChE have the D70G mutation. The apparent inhibition seen at high aspirin concentration was not due to inhibition by excess substrate but to spontaneous hydrolysis of aspirin, causing inhibition by salicylate. The wild-type and D70G enzymes were competitively inhibited by salicylic acid; the D70K enzyme showed a complex parabolic inhibition, suggesting multiple binding. The effect of salicylate was substrate-dependent, the D70K mutant being activated by salicylate with butyrylthiocholine as substrate. K m value for wild-type enzyme was lower than for D70 mutants, suggesting that residue 70 located at the rim of the active site gorge was not the major site for the initial encounter aspirin–BuChE complex. On the other hand, the virtual absence of affinity of the W82A mutant for aspirin indicated that W82 was the major residue involved in formation of the Michaelis complex. Molecular modelling of aspirin binding to BuChE indicated perpendicular interactions between the aromatic rings of W82 and aspirin. Kinetic study of BuChE-catalysed hydrolysis of different acetyl esters showed that the rate limiting step was acetylation. The bimolecular rate constants for hydrolysis of aspirin by wild-type, D70G and D70K enzymes were found to be close to 1×10 6 M −1 min −1. These results support the contention that the electrostatic steering due to the negative electrostatic field of the enzyme plays a role in substrate binding, but plays no role in the catalytic steps, i.e. in the enzyme acetylation.

Protein binding of aspirin and salicylate measured by in vivo ultrafiltration.

Methods for measuring protein binding of drugs generally require direct measurement of the concentration of unbound drug and thus may require a highly sensitive assay. In vivo ultrafiltration has been used to determine protein binding of endogenous substances. We have examined its value for measuring protein binding of drugs because it requires measurement of only the concentration of total drug, not unbound drug, in plasma. The protein binding of aspirin and its metabolite salicylate was measured in 29 healthy subjects 20 minutes after a single oral dose of 600 mg soluble aspirin, by the new method, in vivo ultrafiltration, as well as by a standard method, in vitro ultracentrifugation. The data for salicylate were examined systematically to determine the optimal method of determining estimates of protein binding by in vivo ultrafiltration. Estimates of protein binding of salicylate were 81.7% +/- 10.1% (mean +/- SD) by the in vivo method and 81.6% +/- 11.3% by in vitro ultracentrifugation. Bland-Altman analysis of agreement showed that within-individual differences in percentage of protein binding determined by the two methods did not differ significantly from zero (mean difference, 0.07%; 95% confidence interval, -2.33 to +2.46). There was a highly significant correlation between estimates of protein binding by the two methods (r = 0.82; p = 0.001). Protein binding of aspirin was estimated of protein binding by the two methods (r = 0.82; p = 0.001). Protein binding of aspirin was estimated at 58.3% +/- 9.6% by in vivo ultrafiltration and could not be estimated by in vitro ultracentrifugation because the concentration of unbound aspirin in plasma was below the limit of detection for the assay. In vivo ultrafiltration can be used to measure protein binding of drugs and has potential advantages over conventional methods. A sensitive assay may not be required because the unbound drug need not be measured, measurement in vivo may maintain more physiologic conditions, and it may be useful in measuring protein binding of drugs that are degraded rapidly in vitro.

Maternal Perfusion with Low-Dose Aspirin Preferentially Inhibits Placental Thromboxane While Sparing Prostacyclin

Objective: Production sites of thromboxane and prostacyclin are compartmentalized within the human placenta. Thromboxane is produced primarily by the trophoblast cells closest to the maternal circulation, whereas prostacyclin is produced primarily by the endothelial cells closest to the fetal circulation. Theoretically, this arrangement allows for a selective inhibition of placental thromboxane by maternally derived aspirin because according to Fick's Second Law of Diffusion, the concentration of aspirin would decline as it crossed from the maternal to the fetal side, thereby sparing prostacyclin on the fetal side. We hypothesized that perfusion of aspirin on the maternal side of the placenta would result in inhibition of thromboxane with a sparing of prostacyclin.Study Design: To test this, we perfused human placental cotyledons in vitro with low doses of aspirin (5 × 10−-5 mom and 1 × 10−-4 mol/L) from the maternal side and measured the secretion rates of the stable metabolites of thromboxane and prostacyclin (TXB2 and 6–keto-PGF1α respectively). We also determined the transport of aspirin across the placenta.Results: Only 34% of the aspirin perfused on the maternal side crossed to the fetal side, providing proof of Fick's Second Law of Diffusion for the transport of aspirin across the human placenta. Compared to the control, perfusion of aspirin on the maternal side of the placenta preferentially inhibited the secretion of thromboxane while sparing prostacyclin. The total placental secretion rate of TXB2 was decreased by 48.8% by aspirin at a concentration of 5 × 10−-5 mom and by 80.2% at a concentration of 1 × 10−-4 mom. In contrast, the secretion rate of 6–keto-PGF1α was decreased by only 4.2% and 21.5% by these concentrations of aspirin. The placental secretion rate ratio of TXB, to 6–keto-PGF1α decreased from 14.9 for the control to 7.9 and 3.8 with each dose of aspirin, respectively. There were no changes over time in maternal or fetal secretion rates of thromboxane or prostacyclin for placental cotyledons perfused without aspirin.Conclusions: The compartmentalization of thromboxane and prostacyclin synthesis within the human placenta provides an arrangement whereby low doses of maternally derived aspirin can preferentially inhibit thromboxane because as aspirin crosses from the maternal to the fetal side, the higher concentrations of aspirin on the maternal side inhibit thromboxane in the trophoblast cells, but as aspirin crosses, its concentrations decline, so prostacyclin synthesis by the endothelial cells on the fetal side is spared. This is a beneficial effect of low-dose aspirin therapy for the prevention of preeclampsia.

Effect of aspirin on cell proliferation and differentiation of colon adenocarcinoma Caco‐2 cells

Several lines of evidence suggest that long-term treatment with non-steroidal anti-inflammatory drugs may reduce the risk of colon cancer and the size and number of colonic polyps in patients with familial adenomatous polyposis. Aspirin has also been shown to inhibit cell proliferation in human tumor cell lines and to induce apoptosis in colonic mucosa of familial polyposis patients. To elucidate the molecular mechanisms of the antiproliferative action of aspirin, we studied the effects of aspirin on cell growth and differentiation of the human colon carcinoma Caco-2 cell line. These cells represent a useful tool for studying the mechanisms involved in the regulation of cell growth and differentiation of intestinal epithelial cells since they spontaneously differentiate into polarized cells, expressing brush border enzymes. We show in this study that aspirin (0.1–10 mM) induces a profound inhibition of cell replication as assessed either by cell counts or thymidine incorporation. Moreover, aspirin concentrations of 5 and 10 mM induce apoptosis, whereas concentrations of 1 and 2 mM do not. The inhibition of growth is associated with a dose-dependent reduction in insulin-like growth factor II mRNA expression and with an increase in sucrase activity (a brush border enzyme) and apolipoprotein A-I mRNA expression, 2 specific markers of the differentiative status of this cell line. Our data thus show that aspirin-dependent inhibition of cell growth is associated with the enterocyte-like differentiation of Caco-2 cells. Int. J. Cancer 73:880–884, 1997. © 1997 Wiley-Liss, Inc.

Effect of aspirin on cell proliferation and differentiation of colon adenocarcinoma Caco-2 cells.

Several lines of evidence suggest that long-term treatment with non-steroidal anti-inflammatory drugs may reduce the risk of colon cancer and the size and number of colonic polyps in patients with familial adenomatous polyposis. Aspirin has also been shown to inhibit cell proliferation in human tumor cell lines and to induce apoptosis in colonic mucosa of familial polyposis patients. To elucidate the molecular mechanisms of the antiproliferative action of aspirin, we studied the effects of aspirin on cell growth and differentiation of the human colon carcinoma Caco-2 cell line. These cells represent a useful tool for studying the mechanisms involved in the regulation of cell growth and differentiation of intestinal epithelial cells since they spontaneously differentiate into polarized cells, expressing brush border enzymes. We show in this study that aspirin (0.1-10 mM) induces a profound inhibition of cell replication as assessed either by cell counts or thymidine incorporation. Moreover, aspirin concentrations of 5 and 10 mM induce apoptosis, whereas concentrations of 1 and 2 mM do not. The inhibition of growth is associated with a dose-dependent reduction in insulin-like growth factor II mRNA expression and with an increase in sucrase activity (a brush border enzyme) and apolipoprotein A-I mRNA expression, 2 specific markers of the differentiative status of this cell line. Our data thus show that aspirin-dependent inhibition of cell growth is associated with the enterocyte-like differentiation of Caco-2 cells.

The sensitivity of bovine corneal epithelial lyso-PAF acetyltransferase to cyclooxygenase and lipoxygenase inhibitors is independent of arachidonate metabolites.

Lyso-platelet-activating factor (PAF) acetyltransferase is a critical regulatory step in PAF synthesis. PAF accumulates in the cornea in response to injury and is a potent inflammatory mediator that stimulates corneal cyclooxygenase but not lipoxygenase reactions. 12(S)-hydroxyeicosatetraenoic (HETE) acid, a major lipoxygenase product of mammalian corneas, is also generated during injury. In the bovine corneal epithelium, both PAF acetyltransferase and 12-lipoxygenase are microsomal enzymes. A potential interaction between these two lipid mediators was, therefore, examined. PAF acetyltransferase activity was assayed by determining radioactivity in the trichloroacetic acid-precipitated complex of [3H]PAF bound to albumin, formed after incubation of corneal epithelial microsomes with lyso-PAF and [3H]acetyl CoA. Lipoxygenase metabolism by bovine corneal epithelial microsomes was also studied. While 12(S)-HETE did not activate lyso-PAF acetyltransferase, PAF synthesis was decreased when microsomes were treated with lipoxygenase inhibitors. The IC50 values for nordihydroguaiaretic acid (NDGA), and baicalein were 75 and 105 microM, respectively. The IC50 value for CDC, a more potent inhibitor of platelet 12-lipoxygenase, was greater than 200 microM. The results indicate that concentrations suppressing lyso-PAF acetyltransferase activity exceed those required to inhibit lipoxygenases from bovine corneal epithelia. Similarly, concentrations of aspirin and indomethacin, cyclooxygenase inhibitors that decrease PAF formation, were greater than those reported to block prostaglandin generation. A number of other compounds, some structurally similar to the lipoxygenase inhibitors that suppress lyso-PAF acetyltransferase, and others unrelated chemically but known as anti-oxidant and cationic-chelators, also inhibited lyso-PAF acetyltransferase. This suggests that lyso-PAF acetyltransferase activity is inhibited by mechanisms independent of lipoxygenase and cyclooxygenase metabolites.

Effects of Aspirin on Nitric Oxide Formation andDe NovoProtein Synthesis by RINm5F Cells and Rat Islets

Aspirin and aspirin-like drugs are the most commonly indicated agents for the treatment of inflammation. Mechanisms of action for these drugs, however, are not clearly understood. In this study, we examined the effects of aspirin on production of nitric oxide (NO), a proinflammatory mediator, and show that aspirin inhibits NO production by transformed pancreatic beta cells (RINm5F) and rat islets in a concentration-dependent manner with an IC50 value of approximately 3 mM. Therapeutic concentrations of aspirin (1-5 mM) that block NO production affected neither nuclear factor-kappaB activation nor inducible NO synthase (iNOS) mRNA transcription but potently inhibited iNOS protein expression by both RINm5F cells and rat islets. The effects of aspirin on islet function were examined by measuring glucose-stimulated insulin secretion in the presence of various concentrations of aspirin. Aspirin (1-5 mM) did not affect insulin secretion at basal or glucose-stimulated conditions, whereas higher concentrations of aspirin (10-20 mM) significantly increased basal insulin secretion. Aspirin at high concentrations of 10 and 20 mM inhibited de novo protein synthesis as demonstrated by inhibition of [35S]methionine incorporation into total islet protein and by inhibition of rabbit reticulocyte expression by Brome mosaic virus mRNA, suggesting that inhibition of iNOS expression at these high concentrations of aspirin may be due to the impairment of the translational machinery. These findings indicate that inhibition of iNOS expression and NO production may explain, in part, the beneficial effects of aspirin as an anti-inflammatory agent at therapeutic concentrations, whereas inhibition of de novo protein synthesis may possibly explain clinical and side effects of aspirin in the inflamed tissues and organs such as stomach and kidney that may accumulate high concentrations of aspirin.

Barbiturates and Analgesics in Calliphora vicina Larvae

Abstract Calliphora vicina larvae were reared on artificial foodstuffs spiked with a range of concentrations of aspirin (acetylsalicylic acid), sodium salicylate, paracetamol, sodium aminohippurate, amphetamine sulfate, and the barbiturates thiopentone, phenobarbitone, amylobarbitone, barbitone, and brallobarbitone. Larvae were harvested at either day 6, 7, or 8 for analysis of drug content. Paracetamol, aspirin, amylobarbitone, and thiopentone were not detected in larvae fed on foodstuff containing drug concentrations equivalent to those expected in skeletal muscle from fatal human overdoses. Drug concentrations in larvae (expressed as larva: Foodstuff drug ratio) were 12–14% for phenobarbitone, 9–11% for sodium salicylate, 10% for aminohippurate, 18–19% for brallobarbitone, 41% for amphetamine, and 50–67% for barbitone. Amylobarbitone became detectable in larvae fed on higher drug concentrations (larva: Foodstuff drug ratio 2.6–21%). Higher levels of thiopentone and phenobarbitone were lethal to the larvae. Despite sharing similar basic structures, related drugs were each handled very differently by the larvae. We found it impossible to predict, on the basis of chemical structure, which drugs are likely to be detectable in Calliphora vicina larvae and in what ratio to the drug-spiked foodstuff. Drug concentrations in larvae are significantly lower than in their food source and the absence of a drug from feeding larvae does not necessarily imply its absence from the food source.

Uncoupling effects of diclofenac and aspirin in the perfused liver and isolated hepatic mitochondria of rat

Gluconeogenesis, glycolysis and glycogenolysis were studied in rat perfused liver following the infusion of various concentrations of diclofenac and aspirin, two non-steroidal anti-inflammatory drugs (NSAIDs). Glucose synthesis was measured in livers isolated from 48-h fasted rats perfused with Krebs-Henseleit bicarbonate buffer containing l-lactate (2 mM) and pyruvate (0.1 mM) as precursors. Both diclofenac (0.01–0.1 mM) and aspirin (1–10 mM) had an inhibitory effect on gluconeogenesis (GNG). The inhibition was dose-dependent and reversible. For the estimation of glycogenolysis and glycolysis, the rates of glucose release and of lactate and pyruvate production were measured in livers of well-fed rats perfused with substrate-free buffer. Infusion of diclofenac (0.1 mM) or aspirin (5 mM) strongly stimulated glycogenolysis and glycolysis (GGL/GL). In general, an increased oxygen consumption by the liver tissue was also noted in both types of experiments, as deduced from the continuous monitoring of oxygen concentration changes in the effluent. Such a pattern of response can be attributed to the uncoupling effects of the two drugs on oxidative phosphorylation. Measurements of respiration rates and membrane potential in isolated liver mitochondria submitted to various concentrations of diclofenac and aspirin confirms this assumption. Thus, 0.01 to 0.2 mM diclofenac stimulates state-4 respiration and slightly inhibits state 3, decreasing the respiratory control ratio, while the membrane potential is decreased or collapsed (depending on the drug concentration). Similar effects are recorded for aspirin at higher concentrations (0.2–5 mM), even though state 3 is not affected in this case. Arguments are presented that the concentrations of the drugs used largely correspond to the pharmacological doses employed in antipyretic and anti-inflammatory treatments. Therefore, a greater consideration should be given to the uncoupling effect, at least from the toxicological viewpoint.

Rapid and Selective Ultraviolet Spectrophotometric Assay of Aspirin in Complex Tablet Formulations

Abstract A simple UV spectrophotometric technique was developed for rapid estimation of aspirin in complex tablet formulations. The method is based on measurement of the change in absorbance at 302 nm due to formation of salicylic acid during hydrolysis of aspirin in 0.09N NaOH. The change in absorbance follows a linear relationship with aspirin concentration in the range of 10–50 μg/mL. The method was applied to various complex tablet formulations. Recoveries of aspirin from these formulations, excipients, additives, and active ingredients confirmed the applicability of the method to complex aspirin formulations.

Computer program for the determination of salicylic acid content in aspirin by derivative spectrometry

A mathematical program in Turbo Pascal 6.00, which is enable to generate spectra and to obtain first and second order derivative spectra, is proposed. The second order derivative spectrum of salicylic acid showed a trough at 292 nm and a satellite peak at 316 nm. When large amounts of aspirin coexisted, the trough disappeared, but the height of satellite peak ( D) was not altered even at an aspirin concentration which was 2000 times more than that of salicylic acid (corresponding to salicylic acid content of 0.05%). The results were compared with those obtained by using a spectrophotometer for recording the second order derivative spectrum of aspirin.

Novel actions of aspirin and sodium salicylate: discordant effects on nitric oxide synthesis and induction of nitric oxide synthase mRNA in a murine macrophage cell line.

Aspirin and sodium salicylate each inhibit to a similar extent the production of nitric oxide (NO) in the RAW 264.7 murine macrophage cell line following stimulation by either lipopolysaccharide (LPS) or interferon-gamma (IFN-gamma). The similar potencies of aspirin and sodium salicylate indicate that acetylation of cellular macromolecules is not essential for the observed effects. The failure of added prostaglandin E2 to overcome the effects of aspirin or sodium salicylate indicates that these effects are not simply the result of inhibition of prostaglandin synthesis. The inhibition of NO production occurs irrespective of the effect of these agents on induction of nitric oxide synthase (iNOS) mRNA by LPS or IFN-gamma. Aspirin and sodium salicylate inhibit iNOS mRNA induction in LPS-stimulated cells but enhance iNOS mRNA induction in IFN-gamma-stimulated cells. In contrast, these agents consistently inhibit induction of argininosuccinate synthetase mRNA in both LPS- and IFN-gamma-stimulated cells. Concentrations of aspirin in the 3-10 mM range inhibit induced NO production and expression of iNOS protein without inhibiting induction of iNOS mRNA. Discordances between effects on NO synthesis and induction of iNOS mRNA indicate that aspirin and sodium salicylate have multiple sites of action in their effects on pathways that are involved in the production of NO by stimulated RAW 264.7 cells.

Aspirin-DNA interaction studied by FTIR and laser Raman difference spectroscopy

The interaction of calf-thymus DNA with aspirin is investigated in aqueous solution at pH 7-6 with drug/DNA(phosphate) molar ratios of r = 1/40, 1/20, 1/15/ 1/2, 1 and 2. Fourier transform infrared (FTIR) and laser Raman difference spectroscopy are used to determine drug binding sites, sequence preference and DNA secondary structure, as well as the structural variations of aspirin-DNA complexes in aqueous solution. Spectroscopic evidence showed that at low aspirin concentration ( r = 1/40), drug-DNA interaction is mainly through the backbone PO 2 groups and the A-T base pairs. Such interaction largely perturbs the phosphate vibration at 1222 cm −1 and the A-T bands at 1663 and 1609 cm −1 with no major helix destabilization. At higher drug concentration ( r > 1/20), the participation of the G-C bases in drug-DNA complexation was evident by strong perturbations of the guanine and cytosine vibrations at 1717 and 1494 cm −1, with a partial helix destabilization. A major alteration of the B-DNA structure towards A-DNA occurs on drug complexation. The aspirin interaction was through anion CO and COOCH 3 donor atoms with those of the backbone PO 2 group and DNA bases donor sites (directly or indirectly via H 2O molecules).

Involvement of (n-6) essential fatty acids and prostaglandins in liver lipid accumulation in Japanese quail

Abstract Objective To investigate the involvement of (n-6) essential fatty acids, such as linoleic acid [18:2(n-6)] or γ-linolenic acid [18:3(n-6)], and of prostaglandins on liver lipid accumulation in Japanese quail. Design Effects of graded amounts of aspirin, which inhibits prostaglandin synthesis, on liver weight were determined in experiment 1. Experiment 2 was designed to clarify the effect of dietary essential fatty acid sources and inhibition of prostaglandin synthesis on the liver fat and fatty acid profile. Animals Female Japanese quail. Procedure In experiment 1, from 1 to 3 weeks of age, birds were fed ad libitum the essential fatty acids-free or linoleic acid-adequate (2%) diets with graded amounts of aspirin (0, 0.1, 0.2, and 0.4%). In experiment 2, from 1 to 4 weeks of age, birds were fed the same amount of essential fatty acids-free, linoleic acid-adequate, or γ-linolenic acid (0.4%) diets with (0.2%) or without aspirin. Results In experiment 1, in groups given the essential fatty acids-free diet, liver weight increased with an increase in dietary aspirin concentration. In experiment 2, γ-linolenic acid completely prevented liver triacylglycerol and cholesterol accumulation induced by the essential fatty acids-free diet. Aspirin treatment significantly lowered plasma prostaglandin F2α concentration, but did not affect liver lipid concentrations. In groups fed the essential fatty acids-free diets, however, aspirin treatment increased liver weight and liver triacylglycerol concentration by 20 and 40%, respectively. Conclusions γ-Linolenic acid or its metabolites, but not linoleic acid itself, are important factors in reducing fatty liver in Japanese quail with the essential fatty acids-deficient condition.(Am J Vet Res 1996;57:342-345)