Demonstration of the myotoxic effect of theophylline on the isolated kidney glomerulus of the rat]

After confirmation of the intense and very fast myorelaxant effect of theophylline on isolated glomeruli, xanthic reagent myotoxic effects are shown during more or less long contacts with these glomerular suspensions. We studied isolated glomeruli diameter evolution according to reagent dose (0,25 to 10 mg/ml) and its contact length (1, 5, 10 minutes). If the diameter remains practically constant during all the period for the lowest doses, it begins to decrease after the 5th minute for higher (1 and 2,5 mg/ml) and cracks up in the first minutes for the biggest ones (5 and 10 mg/ml). Pharmacologic and toxic actions are discussed ; hypothesis of a toxic effect at smooth muscular cells level is proposed.     

Urinary excretion of methylated purines in man and in the rat after the administration of theophylline

Chromatographic characteristics of urinary metabolites of theophylline were studied by two-dimensional thin-layer chromatography, high-performance liquid chromatography and gas chromatography—mass spectrometry. Quantitative data for the urinary metabolites of theophylline in asthmatic children are given. It was shown that 1,3-dimethyluric acid is the predominant excretory product. In addition, smaller amounts of 1-methyluric acid, 3-methylxanthine and unchanged theophylline were found.Excretory patterns after theophylline ingestion before and during the administration of allopurinol in asthma patients and in rats suggest the existence of three metabolic pathways of theophylline. The administration of this drug to a patient with xanthine oxidase deficiency resulted in the excretion of 1-methyluric acid in addition to 1,3-dimethyluric acid, 3-methylxanthine, 1-methylxanthine and unchanged theophylline. It was concluded that in man the oxidation of theophylline is not catalysed by xanthine oxidase.     

Effects of enprofylline and theophylline may show the role of adenosine

It is well established that at low and clinically relevant concentrations theophylline (and caffeine) exerts antagonism at cell surface receptor sites for adenosine. However, it is not known which actions of theophylline are due to adenosine antagonism, because theophylline apparently activates other cellular mechanisms at the same low concentrations. Investigations into the actions of xanthines and their structure activity relationships have identified xanthine compounds like enprofylline (3-propylxanthine) that only has some actions in common with theophylline and that has a negligible ability to antagonize adenosine. Enprofylline is a more potent smooth muscle relaxant and antiasthmatic drug than theophylline but does not produce, e.g., theophylline-like diuretic effects, CNS-stimulant behavioural effects (restlessness - seizures), gastric secretory effects and release of free fatty acids. It is proposed that pharmacodynamic dissimilarities between enprofylline and theophylline may indicate physiological roles of adenosine.     

Effect of substances that alter the level of intracellular cAMP on the reaction of human lymphocytes blast transformation]

Effects of cholera toxin, cholera anatoxin, theophylline and dibutyryl cyclic AMP (db-cAMP) on the PHA-induced DNA synthesis have been studied. It was shown that toxin, db-cAMP and theophylline suppressed mitogen-induced 3H-TdR incorporation and blast-transformation in a dose-related manner. When both toxin and theophylline were given together to PHA-stimulated lymphocytes, the inhibitory effects of these two agents were additive. The inhibitory effects of db-cAMP and theophylline were additive too. This inhibitory effects could be due to the elevation of intracellular cAMP. Cholera anatoxin exerted an inhibitory action on the PHA-stimulated lymphocytes. The inhibitory effects on lymphocyte DNA synthesis by anatoxin and theophylline were not additive. These results suggest that the effects of cholera toxin are mediated by cyclic AMP, but effects of cholera anatoxin may be associated with some other mechanism.     

A novel fluorescent aptasensor for the detection of theophylline based on cryonase-driven signal amplification strategy

In the study, we have developed an expedient and efficient method for the detection of theophylline based on the amplification of the signal intensity of fluorescence based on oxidized single-walled carbon nanohorns (oxSWCNHs)/cryonase. When theophylline was not present in the system, oxSWCNHs can adequately adsorb nucleic acid probes labeled by carboxyfluorescein (FAM). In the presence of theophylline, the nucleic acid probe forms the tertiary probe–theophylline complex, which detaches from the surface of the oxSWCNHs. Then, upon reaction with cryonase, the complex can release the FAM and theophylline into the next cycle. The fluorescence signal of the system exhibits a 1:N magnification, enabling quantitative detection of theophylline. The linear range was 30–150 ng/mL, and the limit of detection (LOD) was 6.04 ng/mL. At the same time, it can also be used to detect theophylline in mouse serum.     

Preparation of Controlled-Release Fine Particles Using a Dry Coating Method

Wet coating methods use organic solvents to prepare layered particles that provide controlled-release medications. However, this approach has disadvantages in that it can cause particle agglomeration, reduce pharmaceutical stability, and leave residual organic solvents. We used a dry coating method to overcome these issues. Fine particles (less than 50 μm in diameter) of controlled-release theophylline were created using theophylline (TP; model drug), polyethylene glycol 20,000 (PEG; drug fixative), hydrogenated castor oil (HCO; controlled-release material), hydrogenated rapeseed oil (HRSO; controlled-release material), and cornstarch (CS; core particle). An ultrahigh-speed mixer was employed to mix TP and CS for 5 min at 28,000 rpm. Subsequent addition of PEG produced single-core particles with a drug reservoir coating. Addition of HCO and HRSO to these particles produced a controlled-release layer on their surface, resulting in less than 10% TP dissolution after 8 h. We successfully demonstrated that this dry coating method could be used to coat 16-μm CS particles with a drug reservoir layer and a controlled-release layer, producing multi-layer coated single-core particles that were less than 50 μm in diameter. These can be used to prepare controlled-release tablets, capsules, and orally disintegrating tablets.     

Studies of phosphodiesterase effects on adipose tissue metabolism in obese subjects by the microdialysis technique.

The effect of non-selective (theophylline) inhibition of cyclic AMP breakdown on norepinephrine stimulated lipolysis rate was investigated in subcutaneous adipose tissue of obese subjects. In addition, changes in interstitial glucose and lactate concentration were assessed by means of the microdialysis technique. The interaction of endogenous released insulin and theophylline on adipocyte metabolism was determined. Theophylline and norepinephrine alone increased glycerol outflow significantly. When both agents were perfused in combination, interstitial glycerol concentration increased further. The enhanced glycerol level due to theophylline application was slightly decreased by insulin. In the presence of theophylline, extracellular glucose concentration increased, in contrast to the catecholamine. Norepinephrine decreased interstitial glucose level. When both drugs were added in combination, the level of interstitial glucose increased to about 1 mM, greater than with theophylline alone. With each intervention, lactate was synthesized. Local adipose tissue blood flow was increased by theophylline and theophylline plus norepinephrine. In conclusion, post-receptor mechanisms increased norepinephrine maximal stimulated lipolysis rate in subcutaneous adipose tissue. Glucose uptake was inhibited by the non-specific inhibitor of phosphodiesterase. The effect of insulin on inhibition of lipolysis was modest but sustained in the presence of high theophylline (10(-4) M) concentration. Phosphodiesterase activity may be relatively low in obese subjects in comparison with lean subjects. In lean subjects theophylline caused a transient reversal of the antilipolytic effect of insulin.     

Role of cAMP in the mechanism of the fever reaction

It has been shown that accumulation of endogenous cAMP caused by theophylline increases the body sensitivity to the minimum doses of leukocytic and bacterial pyrogens and to prostaglandin E1. The increasing effect of theophylline was abolished by administering the higher doses of the pyrogenic agents. Repeated daily administration of bacterial pyrogen in conjunction with theophylline does not induce the development of tolerance. The possible reasons for enhanced fever in response to the minimum doses of the pyrogenic agents during accumulation of endogenous cAMP are discussed.     

Acetic acid improves the sensitivity of theophylline analysis by gas chromatography-mass spectrometry

In the analysis of theophylline by gas chromatography-mass spectrometry (GC-MS), we found that the addition of acetic acid to the solvent (ethyl acetate) decreased the adsorption of theophylline to the glass wool packed into the inlet liner. The addition of acetic acid to ethyl acetate improved the sensitivity for theophylline (optimum concentration of 3%). This simple and sensitive method without derivatization can be applied to the quantification of theophylline in serum samples in clinical and toxicological practice.     

Role of a heterogeneous free state in the formation of a specific RNA-theophylline complex

The helical regions of RNA are generally very stable, but the single-stranded and loop regions often exist as an ensemble of conformations in solution. The theophylline-binding RNA aptamer forms a very stable structure when bound to the bronchodilator theophylline, but the theophylline binding site is not stably formed in the absence of ligand. The kinetics for theophylline binding were measured here by stopped-flow fluorescence spectroscopy to probe the mechanism for theophylline binding in this RNA aptamer. The kinetic studies showed that formation of the RNA-theophylline complex is over 1000 times slower than a diffusion-controlled rate, and the high affinity of the RNA-theophylline complex arises primarily from a slow dissociation rate for the complex. A theophylline-independent rate was observed for formation of the theophylline-RNA complex at high theophylline concentration, indicating that a conformational change in the RNA is the rate-limiting step in complex formation under these conditions. The RNA-theophylline complex requires divalent metal ions, such as Mg2+, to form a high-affinity complex, and there is a greater than 10000-fold reduction in affinity for theophylline in the absence of Mg2+. This decrease in binding affinity in the absence of Mg2+ results primarily from an increased dissociation rate for the complex. The implications of an ensemble of conformations in the free state of this theophylline-binding RNA are discussed and compared with mechanisms for formation of protein-ligand complexes.     

Improved high-performance liquid chromatographic assay for theophylline in plasma and saliva in the presence of caffeine and its metabolites and comparisons with three other assays

A new ion-pairing reversed-phase high-performance liquid chromatographic assay for theophylline is described which allows the separation of theophylline from 1,7-dimethylxanthine — a metabolite of caffeine which interferes with most theophylline assay procedures. Levels of 1,7-dimethylxanthine equivalent to 3 mg/l theophylline were seen in individuals not taking theophylline but who drank three to four cups of coffee per day. This compound was not seen in individuals abstaining from xanthine-containing foods and beverages.     

Dibutyryl cyclic AMP treatment of 3T3 and SV40 virus-transformed 3T3 cells in aggregates. Effects on mobility and cell contact ultrastructure

The random cell movement of BALB/c 3T3 and SV40 virus-transformed BALB/c 3T3 cells within homogeneous aggregates was studied by observing the degree of penetration of newly attached [3H]thymidine-labeled cells into the interior of the aggregates. The 3T3 cells penetrated into 3T3 aggregates an average of 0.89 cell diameter in 1.5 days, whereas the SV40-3T3 cells penetrated into SV40-3T3 aggregates an average of 3.20 cell diameters in the same time. Treatment of the aggregates with theophylline, theophylline plus prostaglandin E1, or theophylline plus dibutyryl cyclic AMP all decreased the penetration of the SV40-3T3 cells into SV40-3T3 aggregates (2.36, 1.22, and 0.79 cell diameters, respectively). The same treatments had little effect on 3T3 aggregates. The ultrastructure of 3T3 and SV40-3T3 cells in aggregates was examined by transmission electron microscopy. The 3T3 cells in aggregates were surrounded by microvilli and lamellipodia which were in contact with neighboring cells, whereas SV40-3T3 cells were nearly devoid of microvilli and lamellipodia and made contact at broader, less regular surface undulations. Treatment with theophylline plus dibutyryl cyclic AMP resulted in the appearance of microvilli on SV40-3T3 cells and also appeared to increase the area of intercellular contacts in both 3T3 and SV40-3T3 cells. These observations were supported for the surface cells of the aggregates by scanning electron microscopy.     

Acrylic polymeric nanospheres for the release and recognition of molecules of clinical interest

Cross-linked poly(methylmethacrylate-co-methacrylic acid) nanospheres were imprinted with theophylline through template radical polymerisation in diluted acetonitrile solution. This study will focus on the effect of functional monomer nature used (methylmethacrylate and/or methacrylic acid) in the recognition and in the release of template in order to develop a material with combined properties of drug delivery and rebinding for clinical applications. After template extraction the nanospheres showed satisfactory recognition properties (up to 1mg template/g of polymer). Moreover polymers prepared selectively removed theophylline with a theophylline rebinding of 5.1 times higher than that of caffeine, a compound of similar structure. Drug release properties were also satisfactory (up to 95% of loaded theophylline in 7 days).     

Variability of the effects of serum-free medium,dibutyryl-cyclic AMP or theophylline on the morphology of cultured new-born rat astroblasts

The effects of serum deprivation, of dibutyryl-cyclic AMP (dBcAMP) and of theophylline on the morphology of cultured new-born rat astroblasts have been studied using Eagle's basal medium (BME) or Eagle's minimum essential medium (MEM) as culture media. Serum deprivation had no effect on cells cultured in BME, while in MEM, deprivation induced a rapid morphological transformation involving the appearance of multiple processes. This phenomenon was rapidly reversible when serum was again added. In serum-supplemented BME, dB-cAMP (1 mM) and theophylline (1 mM) had no effect. In serum-supplement MEM, theophylline (1 mM) had no effect while dB-cAMP (1 mM) induced a slower and poorly reversible morphological alteration. On the other hand cells in serum-free BME showed multiple processes after addition of dB-cAMP (1 mM) or theophylline (1 mM). This rapid alteration was completely reversed either by removal of dB-cAMP and theophylline or by addition of serum.     

Inhibition of the Na+/H(+)-antiporter by theophylline in growth-arrested monkey kidney cells.

Treatment of monkey kidney CV-1 cells with theophylline leads to growth arrest, with sensitivity to theophylline being greatly increased in the absence of bicarbonate. Theophylline, like amiloride, increases the sensitivity of cells to intracellular acidification and protects cells from acid shock. These observations and direct measurements of 22Na uptake suggest that growth-arresting effects of theophylline are mediated by the Na+/H(+)-antiporter.     

The effect of BaCl2 on intestinal sugar transport in the rat in vitro

The effect of BaCl2 on galactose transport across isolated rat small intestine has been investigated. The addition of 5 mM BaCl2 or theophylline (3 mM) to the bathing solutions increased cell water free sugar accumulation and decreased mucosal to serosal sugar fluxes. However the effects of BaCl2 were smaller than those induced by theophylline. Removal of Ca2+ from the bathing solutions did not modify the response to BaCl2, though the response to theophylline was partially reduced. In the presence of 0.1 mM trifluoperazine, both theophylline and BaCl2 were without effect on sugar transport. These findings are discussed in terms of an effect of Ba2+ on intestinal smooth muscle tone.     

Effect of chronic caffeine administration on theophylline concentrations required to produce seizures in rats

Caffeine as well as the antiasthmatic drug theophylline can cause seizures when administered to humans or animals in excessive doses. Studies on rats have shown rapid development of functional tolerance to caffeine-induced seizures whereas repeated pretreatment with theophylline had no significant effect on the theophylline concentrations required to produce seizures. The purpose of this investigation was to determine whether chronic exposure to caffeine can affect susceptibility to the convulsant effect of theophylline. Rats received caffeine, 40 mg/kg, or solvent twice a day for 7 days as an intravenous injection. On the eighth day, theophylline was infused intravenously until the onset of maximal seizures. At this pharmacologic end point, rats pretreated with caffeine had significantly higher theophylline concentrations in the brain and cerebrospinal fluid than did control (solvent-pretreated) animals. Although the concentration differences were relatively small (approximately 11%), they demonstrate in principle the development of caffeine-induced tolerance to the neurotoxic effect of theophylline. Additional experiments showed that the caffeine effect on theophylline neurotoxicity is not acutely mediated by paraxanthine, a major metabolite of caffeine.     

The clearance of purines from the haemolymph of the cecropia silkmoth

The clearance of adenine, caffeine, guanine, theophylline, and xanthine from the haemolymph of diapausing pupae and pharate adults of Hyalophora cecropia was studied. In all animals caffeine and theophylline persisted, while the other purine bases were cleared within a few days.     

Treatment of nocturnal asthma: the role of sustained-release theophylline and oral beta-2-mimetics

In two double-blind, multiple-dose cross-over studies the therapeutic effects of SR theophylline preparations given once each night (mean 11.2 mg/kg per day) versus twice daily in equal doses (mean 10.3 mg/kg per day) (study I) and SR-terbutaline in equal doses (mean 0.25 mg/kg per day) versus SR theophylline in unequally divided daily doses (mean 5.3 mg/kg morning dose, 10.6 mg/kg evening dose) study II) were compared in 19 patients with nocturnal asthma. At the end of each treatment period drug serum concentrations and PEFR were measured every 2 hr over a 24-hr period. With the twice-daily, equally divided regimen, serum theophylline concentrations were lower at night than during the day (mean 9.4 +/- 0.9 versus 11.3 +/- 1.0 mg/l). With the single evening administration, serum theophylline concentrations were considerably higher at night (Cmax 16.3 +/- 1.4 mg/l) and the circadian variation of PEFR was significantly reduced. PEFR was higher during night and early morning (283 +/- 14 versus 217 +/- 11 l/min, P less than 0.005). During daytime in study II, PEFR values were slightly higher with theophylline than terbutaline. There was no significant difference in peak flow between either treatment during the night and early morning. However, additional use of inhaled beta-2-mimetics because of asthmatic attacks occurred more often during terbutaline (79 times in 8/10 patients) than theophylline treatment (29 times in 5/10 patients). Symptom scores, number of attacks and side-effects clearly favor the theophylline regimen. We conclude that for patients with nocturnal asthma a once-nightly dose of SR theophylline can be sufficient for stabilization of the airways.     

Determination of theophylline in serum and saliva in the presence of caffeine and its metabolites

Because of marked variability in its metabolic clearance and its narrow therapeutic range (10–20 μg/ml) investigation of each patient's clearance of theophylline is desirable. The author reports here a rapid reversed-phase high-performance liquid chromatographic (HPLC) method to determine, within 3 min, the theophylline in serum and saliva in the 0.1–50 μg/ml range. A fast HPLC column, 10 × 4.6 mm, packed with 3-μm spherical ODS packing is used with acetonitrile—methanol—buffer pH 4.7 (4:7:89) to achieve separation of theophylline from paraxanthine and matrix components. Since theophylline is a major pediatric bronchodilator, the feasibility of assay in saliva was investigated as an alternative route for determining the clearance in stressed asthmatic children. Using this method it was found that the ratio of theophylline in simultaneous serum and saliva samples is very consistent over time in the same person (± 3.99%), but inter-individually this consistency is reduced ten-fold. Simultaneous serum and saliva samples need be taken only once to obtain the ratio and the kinetics followed further with salivary samples only.