Angioplasty for the treatment of buttock claudication caused by internal iliac artery stenoses

A case of buttock claudication due to isolated internal iliac artery stenoses is presented. Although ankle systolic pressure at rest was within normal limits and distal pulses were palpable, an angiogram demonstrated severe stenoses. A computed tomography scan showed no spinal stenosis. The patient was successfully treated with angioplasty. This diagnosis may be elusive if ankle pressure or distal pulses are normal, thereby directing the clinician's suspicion away from vascular pathology.

Neuropeptide Y changes the excitability of fine afferent units in the rat knee joint

1. The aim of the present study was to examine the effects of the sympathetic co-transmitter Neuropeptide Y on primary afferent nerve fibres of the rat knee joint. The responses to passive joint rotations at defined torque were recorded from 41 slowly conducting afferent nerve fibres (0.9 - 18.8 m s(-1)) innervating the knee joint capsule. 2. About 70% of the joint afferents were significantly affected in their mechanosensitivity by topical application of Neuropeptide Y. Significant effects occurred at a concentration of 10 nM. 3. Decreased mechanosensitivity was observed in about 40% of nerve fibres, whereas 30% of the units increased the mechanosensitivity. In addition, in about 35% of the fibres resting activity was induced or increased. Neither the conduction velocity nor the mechanical threshold of the units correlated with the described effects of Neuropeptide Y. 4. NPY(13--36), a specific Y2-receptor agonist, only modulated the mechanosensitivity, with no effect on the resting activity. The effects on the mechanosensitivity were similar to Neuropeptide Y, i.e. increase and decrease of the response. 5. Studies with the Y1-agonist (Leu(31), Pro(34))-NPY showed that activation of the Y1-receptor predominantly resulted in an enhanced mechanosensitivity and an induction or increase of a resting activity. The opposite effect was observed by application of BIBP 3226 BS, a Y1-receptor antagonist. 6. In conclusion, these data indicate that Neuropeptide Y affects the excitability of sensory nerve fibre endings.

Responses of fine primary afferent nerve fibres innervating the rat knee joint to defined torque

In total 23 rat knee joint afferent units with conduction velocities of 1.2-17 m/s were recorded extracellularly during inward and outward joint rotations of defined torque using a newly developed torque-meter. There was not a linear relation between the torque and the obtained angle of the joint. The mechanical thresholds of the units ranged from 10 to 60 mNm. During 10 s of stimulation with 60 mNm they responded with 12-300 action potentials. Two mechanosensitive nerve fibres could not be activated via knee joint rotation at any torque at all. The units could be classified according to their response pattern during stimulation: (1) phasic-tonic response behaviour; (2) constant discharge rate; (3) delayed onset of activity. In conclusion, the novel torque-meter allows a precise characterisation of the mechanical threshold and the corresponding response of fine afferent joint units during knee joint rotation.

Galanin influences the mechanosensitivity of sensory endings in the rat knee joint

The aim of the present study was to examine the effect of galanin on group III and IV afferent nerve fibres (n = 53) innervating normal and acutely inflamed knee joints in rats. They responded to local mechanical stimulation, movements of the joint and i.a. injections of KCl close to the joint. Single i.a. bolus injections of galanin (0.1 mM, 0.2 mL) caused no direct responses of the units. In normal and acutely inflamed joints, about half of the units did not change the responses to knee joint rotation. A significant reduction of the responses to noxious movements was found in approximately 40% of the units reaching a mean value of 57% in normal joints and 70% in inflamed joints compared with control movements. In approximately 10% the responses increased to 143% in normal joints and 120% in inflamed joints. Injection of a galanin receptor antagonist (M35) doubled the responses to noxious movements in 36% of the units in normal joints and reduced it in 18% to 86% of the control movements, indicating a tonic release and influence on the mechanosensitivity of a proportion of primary afferents by galanin. In conclusion, these data further support the hypothesis that the mechanosensitivity of fine afferent nerve fibres is regulated by a mixture of different substances being released into the innervated tissue. Besides the action of several pro-inflammatory peptides there seems to exist a tonic inhibitory system.

The control of mandible movements in the ant Odontomachus

Ants use their mandibles to manipulate many different objects including food, brood and nestmates. Different tasks require the modification of mandibular force and speed. Besides normal mandible movements the trap-jaw ant Odontomachus features a particularly fast mandible reflex during which both mandibles close synchronously within 3 ms. The mandibular muscles that govern mandible performance are controlled by four opener and eight closer motor neurons. During slow mandible movements different motor units can be activated successively, and fine tuning is assisted by co-activation of the antagonistic muscles. Fast and powerful movements are generated by the additional activation of two particular motor units which also contribute to the mandible strike. The trap-jaw reflex is triggered by a fast trigger muscle which is derived from the mandible closer. Intracellular recording reveals that trigger motor neurons can generate regular as well as particularly large postsynaptic potentials, which might be passively propagated over the short distance to the trigger muscle. The trigger motor neurons are dye-coupled and receive input from both sides of the body without delay, which ensures the synchronous release of both mandibles.

Effect and outcome of balloon angioplasty and stenting of the iliac arteries evaluated by intravascular ultrasound

OBJECTIVES

To document the mechanism of percutaneous transluminal angioplasty (PTA) and stenting of the iliac arteries, and to relate the effect to patency.

MATERIALS AND METHODS

Thirty-seven stenotic iliac arteries were examined by intravascular ultrasound (IVUS) and arteriography before and after PTA, and after stent deployment (n = 16). The patients were followed prospectively by duplex scanning at 3, 6, 12, 18 and 24 months after the intervention.

RESULTS

The effect of PTA was established by both compression and stretching with the major contribution arising from stretching. There were differences in the effect of PTA dependent on plaque morphology: in homogeneous eccentric lesions, stretching contributed significantly more than compression to the luminal gain, while stretching and compression contributed equally in concentric or heterogeneous plaques. Stenting of the arteries had no effect on the free luminal area as measured by IVUS. The primary 1-year patency rate was 72%. The patency was related to the free luminal area and diameter and the heterogenicity of the plaque as evaluated by IVUS. The arteriographic measurements did not have any predictive value.

CONCLUSION

IVUS was able to document the effect of PTA and stenting in the iliac arteries, and predict the outcome. The luminal gain and reduction in degree of stenosis seemed to be accomplished primarily by stretching of the arteries and to a lesser extent by plaque compression. Stenting did not change the IVUS measurements. Patency was related to the size of the free lumen and the heterogenicity of the plaque.

Quantification of iliac artery stenoses: a methodological comparative study between intravascular ultrasound, arteriography and duplex scanning

Two morphological methods for quantifying the degree of stenoses in the iliac arteries, intravascular ultrasound (IVUS) and arteriography, were compared with duplex scanning, a method of evaluating the haemodynamic importance of the stenosis. A total of 38 patients, 20 women and 18 men, median age 66 y, admitted for either PTA (n=18) or femoro-femoral crossover bypass surgery (n=20), were examined by IVUS, single plane arteriography and duplex scanning. The predictive value, sensitivity, specificity and kappa value of IVUS were higher than the corresponding values for arteriography. Logistic regression analysis found that IVUS had a predictive value (p=0.0003) for diagnosing significant stenosis as defined by duplex scanning, but arteriography did not (p=0.1). However, this difference in usefulness as predictors did not reach significance. The agreement between arteriography and IVUS was relatively good. The conclusion is that IVUS seems to be superior to single-plane arteriography in predicting hemodynamically significant stenoses as defined by duplex scanning.

Mandible muscle fibers in ants: fast or powerful?

Ants use their mandibles for catching prey, cracking seeds, cutting leaves, or for the construction of nests and the tender care of brood. The functional morphology of the mandibles reflect the species' adaptations to particular foraging habits and social life. The versatility and specialization of the mandibles depend directly on the design and physiology of the mandible closer muscles and their component fibers. A comparative video analysis of the closing movements of ant mandibles revealed that the maximal velocity varies considerably among species. The speed is correlated with the morphology of the mandible closer muscle, the largest muscle in ants. It is composed of two morphologically very distinct fiber types: long fibers with short sarcomeres (sarcomere length approximately 2 microM) showing all the structural attributes of fast muscle fibers, and shorter fibers with longer sarcomeres (sarcomere length approximately 5 microM) exhibiting the characteristics of slow and powerful fibers. Ants with fast-moving mandibles have a very high proportion of fast closer fibers, whereas the muscles of ants that cannot perform fast mandible movements have only a few or no fast fibers at all. Fast fibers always attach directly to the solid apodeme, while slow fibers often attach to thin apodeme threads. We suppose that the latter kind of fiber attachment is disadvantageous for fast contracting fibers but helps the ants to make better use of the space in the head capsule.

Importance of diastolic velocities in the detection of celiac and mesenteric artery disease by duplex ultrasound

PURPOSE

To assess the predictive value of ultrasound duplex scanning in the detection of superior mesenteric artery (SMA) and celiac artery (CA) occlusive disease.

METHODS

Thirty-nine patients in whom mesenteric ischemia was suspected were examined with duplex scan and arteriography.

RESULTS

Duplex scan visualized both vessels in all examined patients. An absent Doppler signal from an adequately visualized SMA or CA was a pathognomonic sign for total occlusion of the arteries. Elevated diastolic velocities (peak diastolic velocity > 70 cm/sec for SMA and > 100 cm/sec for CA) were accurate predictors of arteriographically confirmed stenoses > or = 50%. Increased blood velocity was occasionally observed in a thyrotoxic patient with malabsorption-induced weight loss and abdominal pain but arteriographically-normal SMA. Further examinations of hyperthyroid patients showed systematic elevation of peak systolic velocity in the SMA greater than 300 cm/sec but normal diastolic velocities and resistivity indexes.

CONCLUSION

Duplex ultrasound is a highly selective and specific method for detection of SMA and CA occlusive disease. The most accurate predictors of the disease were increased diastolic velocities, which in contrast to peak systolic velocity also correctly classified thyrotoxic patients. The method can be used before arteriographic evaluation as a screening examination of patients in whom mesenteric ischemia is suspected.

Prediction of outcome after femoropopliteal balloon angioplasty by intravascular ultrasound

OBJECTIVE

To evaluate intravascular ultrasound (IVUS) as a control procedure after femoropopliteal percutaneous transluminal angioplasty (PTA), and compare it with arteriography.

DESIGN

Descriptive study.

MATERIAL

Arteriographic and intravascular ultrasound data obtained from 18 patients (20 limbs) undergoing PTA of the superficial femoral or popliteal artery. The degree of stenosis, the diameter and area of the lumen and the morphological changes in the plaque were related to the short-term patency of the intervention, as evaluated by duplex scan and ankle branchial index.

RESULTS

Fifteen arteries remained patent. Two occlusions and two stenoses developed during the first 3 months after the intervention and one occlusion occurred after 1 year. The following IVUS parameters were related to a favourable patency: presence of calcification; dissection or plaque rupture and residual stenosis of less than 70%. The arteriographically determined diameter reduction did not show predictive value.

CONCLUSION

This study shows that in contrast to arteriography, IVUS revealed parameters predictive for patency following PTA.

Changes in superior mesenteric artery Doppler waveform during reduction of cardiac stroke volume and hypotension

Influence of stroke volume reduction and hypotension on the superior mesenteric artery (SMA) Doppler waveform was evaluated during head-up tilt-induced central hypovolemia in 11 healthy volunteers. During normotensive reduction in stroke volume, peak systolic velocity (pV), mean velocity, pulsatility and resistivity indices decreased, while diastolic velocities increased. During hypotension, a further decrease in pV was accompanied by maintained elevation of diastolic velocities and reduction in pulsatility and resistivity indices. Power of backscattered Doppler wave was elevated throughout the hypovolemia. Alterations in pV and pulsatility indices were closely related to changes in stroke volume, and a negative correlation was found between diastolic velocities and stroke volume. regression analysis showed no significant relation between variations in velocity parameters and blood pressure. Results of the study indicate that alterations in stroke volume induce consequential changes in the SMA Doppler waveform. These changes originate from both direct influence of stroke volume and/or pressure on blood flow velocity, and alterations in SMA peripheral resistance that follow variations in stroke volume. Presented interdependencies should be taken into consideration while studying mesenteric physiology with the use of Doppler technique and while interpreting the duplex results in patients suffering from diseases that may influence flow velocity and mimic or obscure Doppler effects of the SMA stenosis.

Acute and chronic effects of winter swimming on LH, FSH, prolactin, growth hormone, TSH, cortisol, serum glucose and insulin

The present investigation is based on a 2.5 months selbstversuch (self-experiment) of the authors, between October 21 1992, and January 6 1993. 11 healthy students, five females and six males, age 24 to 29 years, and their teachers underwent regular winter swimming at least once a week, for 2 to 10 minutes, at the natural water temperature (6.8 degrees C (October 1992) to 2.0 degrees C (January 1993)) in the southern Baltic Sea. Blood samples were drawn before and 30 and 60 minutes after the cold bath, both at the first and the last day of the swimming season. TSH increased from 0.96 mU/l to 1.42 mU/l (p < 0.01) in the untrained, and from 0.93 mU/l to 1.43 mU/l (p < 0.01) in the cold-trained persons, and decreased thereafter (p < 0.01). Similar changes occurred in cortisol serum concentrations, though psychological stress seemed to interfere with cold stress. Cortisol increased from 99 ng/ml to 133 ng/ml in the untrained, and from 101 ng/ml to 137 ng/ml (p < 0.05) in the cold-trained persons within 30 minutes after cold water immersion, and decreased thereafter (p < 0.01). There were mild decreases in prolactin serum levels after cold stress, whereas FSH, LH and growth hormone remained unaltered. There was a mild initial elevation of serum glucose after cold stress (plus 12 mg/dl, (p < 0.01)) which disappeared after training. There were long term training effects besides the effects on glucose: Basal prolactin levels increased by almost the factor two, and insulin serum levels dropped by almost 50%.(ABSTRACT TRUNCATED AT 250 WORDS)

A lupus anticoagulant neutralization procedure using the patient's own platelets

An auto platelet neutralization procedure (APNP) which assists identification of lupus anticoagulants (LA) is described. Patient platelet-rich plasma is frozen then thawed (PRPF) and an activated partial thromboplastin time (aPTT) is performed on both platelet-poor plasma and PRPF. The degree of correction between the two plasmas is calculated and the percentage APNP is obtained. A lupus anticoagulant was suspected if a sample had a prolonged aPTT and at least two out of three of the following characteristics: (1) aPTT resistant to correction with equal parts normal plasma, (2) prolonged kaolin clotting time mixing test (delta KCT), (3) prolonged dilute Russell's Viper Venom Time that did not correct with normal plasma (DRVVR). Ten normal volunteers had mean (+/- SD) APNP of 7.7 +/- 4.3%. Fifty LA negative patients with normal aPTT, delta KCT and DRVVR, had a mean APNP of 10.0 +/- 6.3%. Twenty-eight patients suspected as LA positive had APNP > 25% with a mean of 39.0 +/- 7.5%. Twenty-one patients with prolonged aPTT attributed to factor deficiency had APNP < 25% with a mean of 6.3 +/- 12.0%. LA was also suspected in two other patients with prolonged aPTT that did not meet the above criterion but had APNP > 25%. In three patients with normal aPTT, LA was suspected and APNP ranged from 21 to 28%. An intermediate APNP range of 20-25% may be suggestive of LA in patients with normal aPTT. The APNP did not appear to be effected by platelet count in the samples tested unless the platelet count in PRP was less than 175 x 10(9)/1.(ABSTRACT TRUNCATED AT 250 WORDS)

Duplex ultrasonography of superior mesenteric artery: interobserver variability

The aim of this study was to evaluate the interobserver variability during duplex ultrasonographic investigation of the SMA. Eleven healthy volunteers were examined twice under the same conditions by two independent observers. Three basic Doppler wave parameters were assessed for the SMA: pV, edV, and rT. The tD was recorded for SMA and abdominal aorta (AotD) with B-mode imaging. The interobserver variability was very low for all parameters: pV = 13.5 cm/s; edV = 3.4 cm/s; rT = 0.01 s; tD = 0.3 mm; AotD = 0.5 mm, with corresponding 95% confidence intervals as follows: pV = 19 cm/s; edV = 4.7 cm/s; rT = 0.015 s; tD = 0.4 mm; and AotD = 0.75 mm. Coefficients of variation also showed very low dispersion for results obtained. Under the appropriate standard conditions for duplex sonographic examination of the mesenteric artery, assessments of basic Doppler wave parameters do not differ significantly between independent investigators. Reliable evaluation of B-mode distances can be obtained by replication of measurements.

Clinical pharmacokinetics of the antitumor drug navelbine (5'-noranhydrovinblastine)

Eleven patients with advanced cancer received navelbine (15 mg/m2) as a single i.v. bolus injection. At least 1 week later, the patients were given a 2-fold increased dose of navelbine (30 mg/m2) and, for seven of them, the 30-mg/m2 dose was repeated after a delay longer than a week. After each administration, plasma and urine were collected for 72 h and monitored for navelbine concentration by radioimmunoassay. The comparison of dose-normalized plasma level profiles showed significant time dependence (P less than 0.05) in four of the seven assessable patients. Some patients also exhibited significant (P less than 0.05) nonlinear (dose dependent) kinetic profiles. Only 3 of the 10 appreciable patients were characterized by both time independent and linear profiles. However, the plasma concentration decay curves presented a triphasic shape similar to that obtained with other antitumor Vinca alkaloids and the data were consistent with a three-compartment pharmacokinetic model. The dose and/or time dependence evidenced for most of the patients did not result in marked changes in pharmacokinetic parameters among courses. The pharmacokinetics of navelbine were characterized by a high plasma clearance (0.27 to 1.49 liter.h-1.kg-1), a large distribution volume (8.2 to 48.2 liter.kg-1), and a long terminal half-life (22.1 to 67.8 h). Urine excretion was low (less than 7.9%). Thus, navelbine pharmacokinetics resembles that of other antitumor Vinca alkaloids.

Metabolism of cyclosporin A. I. Study in freshly isolated rabbit hepatocytes

The metabolism of cyclosporin A (CsA), a widely used immunosuppressive agent, was evaluated in freshly isolated rabbit hepatocytes by HPLC which separated CsA from its major group of derivatives, e.g. "first generation" metabolites (monohydroxylated and N-demethylated) and "second generation" derivatives (dihydroxylated and dihydroxy-N-demethylated). After exposure of hepatocytes to radiolabeled CsA (0.5 mg/liter), CsA was rapidly accumulated inside the cells and metabolized. The dihydroxylated metabolites represent the major intracellular forms after 1 hr. CsA metabolites synthesized inside the cells are then rapidly detected in the extracellular compartment. Unchanged drug and the various metabolites are concentrated inside the cells with transmembrane chemical gradients ranging between 20:1 and 40:1. Transport and metabolic processes for CsA have been evaluated over the following CsA extracellular concentration range, 0.1-10 mg/liter. Metabolism appears to be the rate-limiting step. The apparent affinity constant of CsA for the enzyme system involved in its metabolism is approximately 15 microM. Besides the lipophilicity of the molecule, which is responsible for the retention of CsA and its metabolites in the intracellular compartment, the presence of a binding component(s) in the hepatocytes was also demonstrated. CsA and its metabolites seem to have similar affinities for this binding site. These studies demonstrate that CsA is rapidly transformed inside the hepatocytes to various metabolites which may play an important role in the pharmacological activity of the drug and/or in its clinical toxicity.

Metabolism of cyclosporin A. II. Implication of the macrolide antibiotic inducible cytochrome P-450 3c from rabbit liver microsomes

The in vitro metabolism of cyclosporin A (CsA) was investigated by rabbit liver microsomes in order to identify the form(s) of cytochrome P-450 responsible for its biotransformation. Metabolites including monohydroxy-, N-demethylated, dihydroxy- and dihydroxy-N-demethylated derivatives were detected and quantified by HPLC from incubates of liver microsomes, CsA, and NADPH. Kinetic data indicated that monohydroxy- and N-demethylated derivatives were first generated and then served as substrates for production of dihydroxylated derivatives. Liver microsomes from phenobarbital-, beta-naphthoflavone-, triacetyloleandomycin-, erythromycin-, or rifampicin-treated and untreated rabbits were investigated, but only microsomes from animals treated with macrolide antibiotics (specific inducers of form P-450 3c) exhibited a type I binding spectrum upon CsA addition (Ks = 1.5 +/- 0.5 microM) and extensively metabolized the drug to all groups of derivatives (Km = 5.0 +/- 0.5 microM, Vmax = 1.0 +/- 0.2 nmol/mg/min). A linear correlation existed between CsA oxidase activity and P-450 3c specific content. Antibodies to P-450 3c strongly inhibited CsA oxidase activity of microsomes from macrolide antibiotic-induced animals, whereas antibodies to other forms, including P-450 2, 3b, 4, and 6, did not. When highly purified forms of P-450, including P-450 2, 3b, 3c, and 4, were assayed in a reconstituted system, only P-450 3c exhibited type I binding spectrum upon CsA addition (Ks = 1.4 +/- 0.5 microM) and extensively metabolized the drug to all derivatives. We conclude that the macrolide antibiotic-inducible form P-450 3c (or P-450 3c related from(s)) is responsible for the major part of CsA metabolism by rabbit liver microsomes.

Pharmacokinetics of methotrexate and 7-hydroxy-methotrexate after methotrexate infusions

Methotrexate was administered by IV infusion, 2g (1.19 +/- 0.05 g/m2) over 24 hours, to a homogeneous group of patients undergoing treatment for breast cancer. Three courses were given at three week intervals. Methotrexate and 7-hydroxy-methotrexate plasma and urine pharmacokinetics were investigated. The average terminal half-lives of methotrexate and 7-hydroxy-methotrexate in plasma were 15.02 and 15.19 hours respectively. The area under concentration-time curve was 723.8 +/- 196.4 microM x h for methotrexate and 598.1 +/- 212.5 microM x h for 7-hydroxy-methotrexate. The total average urinary excretions of methotrexate and 7-hydroxy-methotrexate over a 96 hour period were 52% and 5.4% respectively. Urinary clearance of methotrexate was 3.46 +/- 1.4 1/h. In contrast, urinary excretion of 7-hydroxy-methotrexate was not linear. These results confirm the protein binding of metabolite to serum albumin and may suggest that distribution of 7-hydroxy-methotrexate is different from unchanged drug or that the metabolite can be eliminated by another route, such as bile.

Chest radiography after minor chest trauma

The results of chest radiography in 581 patients with blunt minor thoracic trauma were reviewed. Frontal and lateral views of the chest indicated pathology in 72 patients (12.4%). Pneumothorax was present in 16 patients; 4 had hemothorax. The physical examination and the results of chest radiography were not in accordance because in 6 (30%) of the 20 patients with hemo/pneumothorax the physical examination was normal. Consequently there is wide indication for chest radiography after minor blunt chest trauma.

Comparative pharmacokinetics of antitumor Vinca alkaloids: intravenous bolus injections of navelbine and related alkaloids to cancer patients and rats

The kinetics of distribution and elimination in rats of the antitumor drug navelbine and of two of its analogues, Na-formyl navelbine and deacetyl navelbine amide, have been studied by radioimmunoassay and compared with the kinetics obtained with vinblastine and vincristine. Fitting to two-exponential curves was used to derive pharmacokinetic parameters. Clearance was found to parallel toxicity for all drugs: it increases from 0.19 1 h-1 kg-1 for vincristine to 0.41 for Na-formyl navelbine, 1.4 for vinblastine, 2.3 for navelbine, and 2.6 for deacetyl navelbine amide. Terminal half-lives were longer for the Na-formyl-substituted alkaloids (around 13 h) than for the others (8-10 h). We have also studied navelbine kinetics in cancer patients entered in recent navelbine clinical trials and found that navelbine pharmacokinetics are characterized by fast and extensive distribution, high clearance (0.92 +/- 0.27 1 h-1 kg-1), and a relatively long terminal half-life (31.2 +/- 4.4 h). Relationships between chemical structure, pharmacokinetic properties, and toxicity or therapeutic efficiency within the Vinca alkaloid series are discussed, together with the relevance of animal models such as the rat in the screening of new antitumor drugs.

Radioimmunoassays of 7-hydroxymethotrexate and methotrexate

Antisera against 7-hydroxymethotrexate were raised in rabbits by injection of 7-hydroxymethotrexate coupled to bovine serum albumin. A 125I-radiolabelled probe was synthesised by radioiodination of 7-hydroxymethotrexate conjugated to tyrosine methyl ester. We developed with these reagents a liquid phase radioimmunoassay for 7-hydroxymethotrexate in which methotrexate did not interfere significantly (cross-reactivity factor = 2.5 X 10(-4]. Similar techniques were used also for the development of a specific radioimmunoassay for methotrexate, which minimally cross-reacted with 7-hydroxymethotrexate. The assessment of the specificity of these assays showed that parallel monitoring of methotrexate and 7-hydroxymethotrexate in human plasma was possible. Coefficients of variation for duplicate determinations were less than 15% between 0.06 and 1.2 nmol/l for methotrexate and between 0.08 and 9 nmol/l for 7-hydroxymethotrexate. Methotrexate and its oxidative metabolite, 7-hydroxymethotrexate, were quantified in plasma of patients following high-dose infusion (2 g over 24 h) by radioimmunoassay and high performance liquid chromatography. The agreement between the two techniques was found satisfactory, as evaluated by least square regression analysis (slopes 1.007 +/- 0.046 for 7-hydroxymethotrexate and 0.937 +/- 0.046 for methotrexate with y-axis intercept not significantly different from zero). These radioimmunoassays permitted also the evaluation of the concentrations of methotrexate and 7-hydroxymethotrexate in plasma after intravenous bolus injection (50 mg/m2), and large inter-individual difference in both methotrexate and 7-hydroxymethotrexate kinetic behaviour could be observed.

High-performance liquid chromatographic analysis of MTX, 7-OH-MTX and MTX derivatives: application to intracellular metabolism in tumor cells (HT 29)

In order to study the intracellular metabolism of Methotrexate (MTX) and the cytotoxicity of the antifolates, a specific paired-ion HPLC method has been developed which permits the simultaneous determination of DAMPA, MTX, 7-OH-MTX, MTX-G1, MTX-G2 and MTX-G3. Cells were incubated with 3H-MTX. The MTX metabolites were extracted, purified on SEP-PAK cartridges and further analysed by high-performance liquid chromatography (HPLC). The stationary phase was constituted by a C18 muBondapak and the mobile phase by 5 mM phosphate buffer (pH 7.4) containing 2.5 mM tetrabutylammonium nitrate. The elution was performed with a linear methanol gradient (20--30%). HPLC fractions were collected and radioactivity evaluated by beta counting (retention times: DAMPA = 12.93 min; MTX = 18.29 min; 7-OH-MTX = 21.13 min; MTX-G1 = 22.69 min; MTX-G2 = 26.81 min; MTX-G3 = 30.61 min). This analytical procedure was applied to separate and characterize multiple forms of MTX polyglutamate derivatives in HT 29, a human adenocarcinoma cell line varying the incubation time (4--18 h) and MTX concentration (0.6--10.6 micrometer). The incorporation process seems to be characteristic of a cell line resistant to MTX. The incorporation were very low and after a 4-h exposure time only 5% of the MTX was converted to polyglutamates. Between 1.6 and 10.6 microM MTX, no difference was observed in the polyglutamization. The defect in the incorporation of the drug and in the metabolization process in vitro could partially explain the failure of the MTX treatment in colorectal cancer.