An injectable, nanostructured implant for the delivery of adenosine triphosphate: towards long-acting formulations of small, hydrophilic drugs.

While long-acting injectable treatments are gaining increasing interest in managing chronic diseases, the available drug delivery systems almost exclusively rely on hydrophobic matrixes, limiting their application to either hydrophobic drugs or large and hydrophilic molecules such as peptides. To address the technological lock for long-acting delivery systems tailored to small, hydrophilic drugs such as anticancer and antiviral nucleoside/nucleotide analogues, we have synthesized and characterized an original approach with a multi-scale structure: (i) a nucleotide (adenosine triphosphate, ATP) is first incorporated in hydrophilic chitosan-Fe(III) nanogels; (ii) these nanogels are then transferred by freeze-drying and resuspension into a water-free, hydrophobic medium containing PLGA and an organic solvent, N-methyl-2-pyrrolidone. We show that this specific association allows an injectable and homogeneous dispersion, able to form in situ implants upon injection in physiological or aqueous environments. This system releases ATP in vitro without any burst effect in a two-step mechanism, first as nanogels acting as an intermediate reservoir over a week, then as free drug over several weeks. In vivo studies confirmed the potential of such nanostructured implants for sustained drug release following subcutaneous injection to mice hock, opening perspectives for sustained and targeted delivery through the lymphatic system.

Acute Effect of Oral Adenosine Triphosphate (ATP) Supplementation on Muscular Performance in Trained Adults.

INTRODUCTION: Adenosine Triphosphate is a molecule with the function of generating energy, where high levels are directly related to cellular and muscular health. Oral supplementation appears as a possibility to guarantee such levels, and is normally consumed in capsules, which can be acute or chronic. OBJECTIVES: To verify the influence of a dose of ATP on muscular performance in adults. METHODS: This is an acute, crossover, randomized, double-blind, placebo-controlled intervention study. 18 trained men were recruited, with an average age of 27.95 years. Two visits were made to the laboratory, where each of the protocols consisted of randomized supplementation of 400 mg of Peak ATP® or placebo, and 30 min later, five series were performed, where the first consisted of five repetitions and the following four of ten repetitions at 60° per second in knee extension and flexion on a Biodex® 4.0 isokinetic dynamometer, where the volunteers' muscle strength and resistance to fatigue were measured. For data analysis, data normality was assessed using Shapiro Wilk, the ANOVA repeated measures test with Bonferroni post hoc. To identify the size of the effect, the Cohen test was performed, and the statistical package used was SPSS 25 with an applied significance of p < 0.05. RESULTS: Acute supplementation was unable to achieve significant improvements in muscle strength indicators. The supplement delays drops in strength as the exercise progresses in knee extension compared to the placebo. CONCLUSIONS: An acute dose of 400 mg of ATP did not improve the volunteers' muscle strength indicators, but it was able to reduce fatigue levels as the exercise progressed, enabling greater performance for longer.

Human safety study of a selective neuronal adenylate cyclase 1 inhibitor NB001 which relieves the neuropathic pain and blocks ACC in adult mice.

Calcium-dependent, neuronal adenylyl cyclase subtype 1 (AC1) is critical for cortical potentiation and chronic pain. NB001 is a first-in-class drug acting as a selective inhibitor against AC1. The present study delineated the pharmacokinetic (PK) properties of human-used NB001 (hNB001) formulated as immediate-release tablet. This first-in-human (FIH) study was designed as randomized, double-blind, placebo-controlled trial. hNB001 showed placebo-like safety and good tolerability in healthy volunteers. A linear dose-exposure relationship was demonstrated at doses between 20 mg and 400 mg. The relatively small systemic exposure of hNB001 in human showed low bioavailability of this compound through oral administration, which can be improved through future dosage research. Food intake had minimal impact on the absorption of hNB001 tablet. Animal experiments further confirmed that hNB001 had strong analgesic effect in animal models of neuropathic pain. In brain slice prepared from the anterior cingulate cortex (ACC), bath application of hNB001 blocked the induction of long-term potentiation (LTP). These results from both rodents and human strongly suggest that hNB001 can be safely used for the future treatment of different types of chronic pain in human patients.

IN VIVO ACTIVATION OF P2Y4 PURINERGIC RECEPTORS USING ATP IN RAT EPIDERMAL TISSUE.

OBJECTIVE: The aim: This study was carried out to examine the presence of P2Y4 receptors in rat epidermal tissue and how their in vivo activation leads to histological and genetic changes. PATIENTS AND METHODS: Materials and methods: Thirty-six Wistar rats were separated into six groups each of six rats, the control group and five injected groups with increasing concentrations of ATP intradermally (0.1, 5.0, 10.0, 50.0, 100.0 µg/ml). The histological and genetic examination was performed from excised tissues. RESULTS: Results: Noticeable histological thickening of the epidermal layer in rats injected with high concentrations of ATP. No apparent histological damage was seen in all injected groups. The genetic expression seems to also increase following exposure to variable concentrations of ATP. CONCLUSION: Conclusions: Purinergic receptors activated by ATP molecules are highly involved in the development of adult tissues. Their precise location within the epidermal layer indicated their importance in cellular proliferation and differentiation of epidermal cells. Excessive exposure to ATP results in their robust genetic ectopic over expression indicative of increased cellular activity.

Contingent intramuscular boosting of P2XR7 axis improves motor function in transgenic ALS mice.

Amyotrophic lateral sclerosis is a fatal neurodegenerative disorder that leads to progressive degeneration of motor neurons and severe muscle atrophy without effective treatment. Most research on the disease has been focused on studying motor neurons and supporting cells of the central nervous system. Strikingly, the recent observations have suggested that morpho-functional alterations in skeletal muscle precede motor neuron degeneration, bolstering the interest in studying muscle tissue as a potential target for the delivery of therapies. We previously showed that the systemic administration of the P2XR7 agonist, 2'(3')-O-(4-benzoylbenzoyl) adenosine 5-triphosphate (BzATP), enhanced the metabolism and promoted the myogenesis of new fibres in the skeletal muscles of SOD1G93A mice. Here we further corroborated this evidence showing that intramuscular administration of BzATP improved the motor performance of ALS mice by enhancing satellite cells and the muscle pro-regenerative activity of infiltrating macrophages. The preservation of the skeletal muscle retrogradely propagated along with the motor unit, suggesting that backward signalling from the muscle could impinge on motor neuron death. In addition to providing the basis for a suitable adjunct multisystem therapeutic approach in ALS, these data point out that the muscle should be at the centre of ALS research as a target tissue to address novel therapies in combination with those oriented to the CNS.

Delivery of membrane impermeable molecules to primary mouse T lymphocytes.

The pore-forming toxin streptolysin-O (SLO) enables intracellular delivery of molecules up to 100 kDa and has been used for short-term delivery of membrane-impermeable substances to assess their effects on cellular activities. A limitation of this technique is the loss of intracellular components and the potential unpredicted alterations of cellular metabolism and signaling. This protocol, optimized for primary mouse T lymphocytes, describes steps for SLO-mediated cell membrane permeabilization and substance supplementation, followed by immunoblotting and immunofluorescent microscopy for assessing cellular effects. For complete details on the use and execution of this protocol, please refer to Xu et al., 2021a, Xu et al., 2021b.

Efficient extra-mitochondrial aerobic ATP synthesis in neuronal membrane systems.

The nervous system displays high energy consumption, apparently not fulfilled by mitochondria, which are underrepresented therein. The oxidative phosphorylation (OxPhos) activity, a mitochondrial process that aerobically provides ATP, has also been reported also in the myelin sheath and the rod outer segment (OS) disks. Thus, commonalities and differences between the extra-mitochondrial and mitochondrial aerobic metabolism were evaluated in bovine isolated myelin (IM), rod OS, and mitochondria-enriched fractions (MIT). The subcellular fraction quality and the absence of contamination fractions have been estimated by western blot analysis. Oxygen consumption and ATP synthesis were stimulated by conventional (pyruvate + malate or succinate) and unconventional (NADH) substrates, observing that oxygen consumption and ATP synthesis by IM and rod OS are more efficient than by MIT, in the presence of both kinds of respiratory substrates. Mitochondria did not utilize NADH as a respiring substrate. When ATP synthesis by either sample was assayed in the presence of 10-100 µM ATP in the assay medium, only in IM and OS it was not inhibited, suggesting that the ATP exportation by the mitochondria is limited by extravesicular ATP concentration. Interestingly, IM and OS but not mitochondria appear able to synthesize ATP at a later time with respect to exposure to respiratory substrates, supporting the hypothesis that the proton gradient produced by the electron transport chain is buffered by membrane phospholipids. The putative transfer mode of the OxPhos molecular machinery from mitochondria to the extra-mitochondrial structures is also discussed, opening new perspectives in the field of neurophysiology.

NMDAR-dependent long-term depression is associated with increased short term plasticity through autophagy mediated loss of PSD-95.

Long-term depression (LTD) of synaptic strength can take multiple forms and contribute to circuit remodeling, memory encoding or erasure. The generic term LTD encompasses various induction pathways, including activation of NMDA, mGlu or P2X receptors. However, the associated specific molecular mechanisms and effects on synaptic physiology are still unclear. We here compare how NMDAR- or P2XR-dependent LTD affect synaptic nanoscale organization and function in rodents. While both LTDs are associated with a loss and reorganization of synaptic AMPARs, only NMDAR-dependent LTD induction triggers a profound reorganization of PSD-95. This modification, which requires the autophagy machinery to remove the T19-phosphorylated form of PSD-95 from synapses, leads to an increase in AMPAR surface mobility. We demonstrate that these post-synaptic changes that occur specifically during NMDAR-dependent LTD result in an increased short-term plasticity improving neuronal responsiveness of depressed synapses. Our results establish that P2XR- and NMDAR-mediated LTD are associated to functionally distinct forms of LTD.

Adenosine triphosphate, polymyxin B and B16 cell-derived immunization induce anticancer response.

Aim: Whole dead tumor cells can be used as antigen source and the induction of protective immune response could be enhanced by damage-associated molecular patterns. Materials & methods: We generated whole dead tumor cells called B16-immunogenic cell bodies (ICBs) from B16 melanoma cells by nutrient starvation and evaluated the in vivo antitumor effect of B16-ICBs plus ATP and polymyxin B (PMB). Results: The subcutaneous immunization with B16-ICBs + PMB + ATP a 50% of tumor-free animals and induced a significant delay in tumor growth in a prophylactic approach. These results correlated with maturation of bone marrow-derived dendritic cells and activation of T CD8+ lymphocytes in vitro. Conclusion: Altogether, ICB + ATP + PMB is efficient in inducing the antitumor efficacy of the whole dead tumor cells vaccine.

Elaidic Acid Potentiates Extracellular ATP-Induced Apoptosis via the P2X7-ROS-ASK1-p38 Axis in Microglial Cell Lines.

trans-Fatty acids (TFAs) are unsaturated fatty acids with at least one carbon-carbon double bond in trans configuration. TFA consumption has been epidemiologically associated with neurodegenerative diseases (NDs) including Alzheimer's disease. However, the underlying mechanisms of TFA-related NDs remain unknown. Here, we show a novel microglial signaling pathway that induces inflammation and cell death, which is dramatically enhanced by elaidic acid (EA), the most abundant TFA derived from food. We found that extracellular ATP, one of the damage-associated molecular patterns (DAMPs) leaked from injured cells, induced activation of the apoptosis signal-regulating kinase 1 (ASK1)-p38 pathway, which is one of the major stress-responsive mitogen-activated protein (MAP) kinase signaling pathways, and subsequent caspase-3 cleavage and DNA ladder formation (hallmarks of apoptosis) in mouse microglial cell lines including BV2 and MG6 cells. Furthermore, we found that in these microglial cell lines, EA, but not its cis isomer oleic acid, facilitated extracellular ATP-induced ASK1/p38 activation and apoptosis, which was suppressed by pharmacological inhibition of either p38, reactive oxygen species (ROS) generation, P2X purinoceptor 7 (P2X7), or Ca2+/calmodulin-dependent kinase II (CaMKII). These results demonstrate that in microglial cells, extracellular ATP induces activation of the ASK1-p38 MAP kinase pathway and ultimately apoptosis downstream of P2X7 receptor and ROS generation, and that EA promotes ATP-induced apoptosis through CaMKII-dependent hyperactivation of the ASK1-p38 pathway, in the same manner as in macrophages. Our study may provide an insight into the pathogenesis of NDs associated with TFAs.

Short-duration, submaximal intensity exercise stress combined with adenosine triphosphate decreases artifacts in myocardial perfusion single-photon emission computed tomography.

BACKGROUND: Myocardial perfusion single-photon emission computed tomography (SPECT) imaging with stress is a useful examination for detecting coronary artery disease. Since the presence of artifacts is remaining challenges, we aimed to define the minimum intensity of low-grade exercise stress levels combined with drug stress to reduce undesired artifacts and their related factors. METHODS: We divided patients with suspicious coronary artery disease into 4 groups as follows: group A, adenosine triphosphate (ATP) for 6 min; group A + 25 W, ATP + 25 W exercise for 6 min; group A + 35 W, ATP + 35 W exercise for 6 min; group A + 45 W, ATP + 45 W exercise for 6 min) and enrolled only those whose summed stress scores were < 3. Undesired artifacts were evaluated on the basis of heart-to-liver activity (H/L) ratio and heart-to-10 pixels below the heart (H/below the H) ratio. RESULTS: The logarithmic values of H/L and H/below the H ratios were significantly higher in groups A + 35 W and A + 45 W than in group A (p < 0.05, each). In all the patients, the logarithmic values of H/L and H/below the H ratios positively correlated with the increment of rate pressure product (RPP, p = 0.002 and p = 0.005, respectively) after stress in the univariate analysis. The left ventricular end-diastolic volume (LVEDV) after stress (p = 0.002) negatively correlated with the logarithmic value of H/below the H ratio, but not H/L ratio. Although the increment of RPP was independently associated with the logarithmic values of both H/L (p = 0.001) and H/below the H ratios (p = 0.005), LVEDV was also independently associated with the logarithmic value of H/below the H ratio (p < 0.001) in multivariate regression analysis under adjusting with age and sex. CONCLUSION: ATP plus ≥35 W exercise stress for 6 min was useful for reducing undesired artifacts after stress in myocardial perfusion SPECT. LVEDV after stress in addition to the increment of RPP was independently associated with the H/below the H ratio, but not the H/L ratio.

Neuronal Adenylyl Cyclase Targeting Central Plasticity for the Treatment of Chronic Pain.

Chronic pain is a major health problem and the effective treatment for chronic pain is still lacking. The recent crisis created by the overuse of opioids for pain treatment has clearly shown the need for non-addictive novel pain medicine. Conventional pain medicines usually inhibit peripheral nociceptive transmission and reduce central transmission, especially pain-related excitatory transmission. For example, both opioids and gabapentin produce analgesic effects by inhibiting the release of excitatory transmitters and reducing neuronal excitability. Here, we will review recent studies of central synaptic plasticity contributing to central sensitization in chronic pain. Neuronal selective adenylyl cyclase subtype 1 (AC1) is proposed to be a key intracellular protein that causes both presynaptic and postsynaptic forms of long-term potentiation (LTP). Inhibiting the activity of AC1 by selective inhibitor NB001 blocks behavioral sensitization and injury-related anxiety in animal models of chronic pain. We propose that inhibiting injury-related LTPs will provide new mechanisms for designing novel medicines for the treatment of chronic pain and its related emotional disorders.

Influence of caffeine intake on intravenous adenosine-induced fractional flow reserve.

BACKGROUND: This study evaluated whether caffeine abstention is required before fractional flow reserve (FFR) measurement by intravenous adenosine triphosphate (ATP) administration in Japanese patients. METHODS: This study was a subanalysis of a previously published study and a total of 208 intermediate lesions that underwent FFR measurements were enrolled for this analysis. Hyperemia was induced by continuous intravenous ATP infusion at 150 µg/kg/min (IVATP150) and 210 µg/kg/min (IVATP210), and by intracoronary administration of nicorandil 2 mg (ICNIC2mg) as a reference standard. RESULTS: The degree of change in the FFR value after ICNIC2mg and IVATP210 was similar between the caffeine and non-caffeine groups (0.00 ± 0.02 vs. 0.01 ± 0.02). In patients who consumed caffeine before the FFR measurement, the degree of FFR change was independent of the time interval (<12 h, 12-24 h, and 24-48 h) between caffeine intake and catheterization both after IVATP150 and ICNIC2mg and after IVATP210 and ICNIC2mg. CONCLUSION: When compared with the FFR value after ICNIC2mg, the degree of change in the FFR value after IVATP210 were similar regardless of caffeine intake. Strict caffeine abstention before intravenous ATP-induced FFR measurement may not be required in clinical practice.

Antiviral treatment using the adenosine nucleoside analogue GS-441524 in cats with clinically diagnosed neurological feline infectious peritonitis.

Feline infectious peritonitis (FIP) is caused by a mutant biotype of the feline enteric coronavirus. The resulting FIP virus (FIPV) commonly causes central nervous system (CNS) and ocular pathology in cases of noneffusive disease. Over 95% of cats with FIP will succumb to disease in days to months after diagnosis despite a variety of historically used treatments. Recently developed antiviral drugs have shown promise in treatment of nonneurological FIP, but data from neurological FIP cases are limited. Four cases of naturally occurring FIP with CNS involvement were treated with the antiviral nucleoside analogue GS-441524 (5-10 mg/kg) for at least 12 weeks. Cats were monitored serially with physical, neurologic, and ophthalmic examinations. One cat had serial magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) analysis (including feline coronavirus [FCoV]) titers and FCoV reverse transcriptase [RT]-PCR) and serial ocular imaging using Fourier-domain optical coherence tomography (FD-OCT) and in vivo confocal microscopy (IVCM). All cats had a positive response to treatment. Three cats are alive off treatment (528, 516, and 354 days after treatment initiation) with normal physical and neurologic examinations. One cat was euthanized 216 days after treatment initiation following relapses after primary and secondary treatment. In 1 case, resolution of disease was defined based on normalization of MRI and CSF findings and resolution of cranial and caudal segment disease with ocular imaging. Treatment with GS-441524 shows clinical efficacy and may result in clearance and long-term resolution of neurological FIP. Dosages required for CNS disease may be higher than those used for nonneurological FIP.

Application of the adenosine triphosphate sensitivity assay in infantile vascular anomalies.

BACKGROUND: The term vascular anomalies include various vascular tumors and vascular malformations, among them infantile hemangiomas and capillary malformations are the most well-known associated diseases in early ages. Multiple drugs have been introduced for intervention, but susceptibility test in vitro were scarcely reported. OBJECTIVE: To evaluate the inhibition effect of different drugs by adenosine triphosphate sensitivity assay in vitro before the treatment of infantile hemangiomas and capillary malformations. METHODS: Specimens were selected from 5 cases of infantile hemangiomas and 11 cases of capillary malformations. Propranolol, rapamycin, sildenafil and itraconazole were tested for their growth inhibition effect by using the adenosine triphosphate sensitivity assay. RESULTS: Propranolol demonstrated inhibitory effects on infantile hemangiomas cells. Rapamycin and itraconazole both showed inhibitory effects on infantile hemangiomas cells and capillary malformations cells. Sildenafil has no growth inhibitory effect on infantile hemangiomas cells or capillary malformations cells. CONCLUSION: Adenosine triphosphate sensitivity assay is a sensitive and useful testing method before the management of vascular anomalies, and individualized medication suggestions for the choice of therapeutic drugs were offered based on the testing result and together with a comprehensive evaluation of each infant.

Effect of QTU prolongation on hyperemic instantaneous wave-free ratio value: a prospective single-center study.

We hypothesized that in patients with QT prolongation, resistance might not decrease in the wave-free period, because QTU prolongation cannot be detected by instantaneous wave-free ratio (iFR) analysis software. We investigated whether corrected QTU (QTUc) prolongation affects the hyperemic iFR value. Forty-two consecutive patients with intermediate stenosis (≥ 50%) in the left anterior descending coronary artery (LAD) were analyzed. Fractional flow reserve (FFR) and hyperemic iFR were simultaneously and continuously recorded with intravenous adenosine triphosphate (ATP) and papaverine infusions. In 17 patients with stenosis in the proximal LAD, coronary flow was measured. Patients were divided into two groups according to the median absolute deviation of the QTUc by ATP administration/QTUc by papaverine administration. FFR, hyperemic iFR, and flow data were compared between each stimulus and group. Moreover, influences of pressure and electrocardiogram parameters on differences in iFR values under ATP and papaverine administration were compared between the following two groups (group 1: the absolute difference of hyperemic iFR values between ATP and papaverine administration is ≤ 0.05; group 2: that is > 0.05). The paired t test and t test were used in analysis. Hyperemic iFR values of patients under the use of papaverine were lower than those of patients under the use of ATP when QTUc was more prolonged by papaverine administration than by ATP administration (ATP 0.74 ± 0.14, papaverine 0.71 ± 0.15, P = 0.025). No significant differences were observed in the FFR value and flow data between the groups. Regarding QTU, QTUc, and QTUc by ATP/QTUc by papaverine, significant differences were observed between group 1 and group 2. Pressure parameters did not induce significant differences. QTUc prolongation induced by papaverine was associated with lower hyperemic iFR values. An iFR-based assessment might lead to inappropriate treatment of patients with QTUc prolongation.

Myocardial blood flow analysis of stress dynamic myocardial CT perfusion for hemodynamically significant coronary artery disease diagnosis: The clinical value of relative parameter optimization.

BACKGROUND: The methods for calculating the optimal myocardial blood flow (MBF) relative parameters in stress dynamic myocardial CT perfusion (CTP) in the detection of hemodynamically significant coronary artery disease (CAD) are non-uniform and lack standards. METHODS: A total of 86 patients who were prospectively recruited underwent APT stress dynamic myocardial CTP. The relative MBF perfusion parameters were calculated as av_Ratio, Q3av_Ratio and hi_Ratio according to the three types of reference MBF values, respectively: (1) average segmental MBF value, (2) the third quartile of the average segmental MBF value, and (3) highest segmental MBF value. All the data were derived from both the endocardial and transmural layers of the myocardium. Invasive coronary angiography and fractional flow reserve (ICA/FFR) were used as the reference standards for myocardial ischemia evaluation. RESULTS: A total of 151 vessels of 60 patients (43 men and 17 women; 61.38 ±â€¯8.01 years) were enrolled in the analysis. The performance of the endocardial layer was superior to that of the transmural layer (all P < 0.05). The hi_Ratio of the endocardial myocardium (AUC = 0.906, 95% CI: 0.857-0.954), for which the highest segmental value was selected as the reference MBF, was superior to both av_Ratio and Q3av_Ratio for ischemia detection (AUC, 0.906 vs.0.879, P < 0.05; 0.906 vs.0.891, P = 0.18), and the sensitivity, specificity, PPV, NPV and diagnostic accuracy were 74.1%, 93.6%, 87.8%, 85.3% and 86.1%, respectively. The cutoff value of hi_Ratio was 0.675. CONCLUSIONS: The relative MBF parameter of the endocardial myocardium using the highest segmental MBF value as a reference provided optimal diagnostic accuracy for the detection of hemodynamically significant CAD.

Rapid-onset vasodilator responses to exercise in humans: Effect of increased baseline blood flow.

NEW FINDINGS: What is the central question of this study? What is the effect of an elevated baseline blood flow, induced by high-dose intra-arterial infusion of either adenosine or ATP, on the rapid-onset vasodilatory response to a single forearm muscle contraction? What is the main finding and its importance? The peak response to a single contraction is unaffected by augmented baseline blood flow, and thus, is likely to be attributable to a feedforward vasodilatory mechanism. ABSTRACT: The hyperaemic responses to single muscle contractions are proportional to exercise intensity, which, in turn, is proportional to tissue metabolic demand. Hence, we tested the hypothesis that the rapid-onset vasodilatory response after a single muscle contraction would be unaffected when baseline blood flow was increased via high-dose intra-arterial infusion of either adenosine (ADO) or ATP. Twenty-four healthy young participants (28 ± 1 years) performed a single forearm contraction (20% maximal voluntary contraction) 75 min after commencement of a continuous infusion of ADO (n = 6), ATP (n = 8) or saline (control; n = 10). Brachial artery diameter and blood velocity were measured using Doppler ultrasound. Resting forearm vascular conductance (FVC; in millilitres per minute per 100 mmHg per decilitre of forearm volume) was significantly higher during ADO (33 ± 17) and ATP infusion (33 ± 17) compared with the control infusion (8 ± 3; P < 0.05). The peak FVCs post-contraction during ADO and ATP infusions were significantly greater than during the control infusion (P < 0.05), but not different from one another. The peak change in FVC from baseline was similar in all three conditions (control, 14 ± 1; ADO, 24 ± 2; and ATP, 23 ± 6; P = 0.15). Total FVC (area under the curve) did not differ significantly between ADO and ATP (333 ± 69 and 440 ± 125); however, total FVC during ATP infusion was significantly greater compared with the control value (150 ± 19; P < 0.05). We conclude that the peak response to a single contraction is unaffected by augmented baseline blood flow and is therefore likely to be attributable to a feedforward vasodilatory mechanism.

Effectiveness and safety of intracoronary papaverine, alprostadil, and high dosages of nicorandil and adenosine triphosphate for measurement of the index of coronary microcirculatory resistance in a pig model.

BACKGROUND: Papaverine is used to induce maximal hyperemia for index of coronary microcirculatory resistance (IMR) measurement in animal experiments, although it can lead to polymorphic ventricular tachycardia and ventricular fibrillation. OBJECTIVES: This study investigated the effect of an intracoronary (IC) bolus of high adenosine triphosphate (ATP) and nicorandil doses for IMR measurement and explored the possibility of inducing maximal hyperemia with an IC alprostadil bolus. MATERIAL AND METHODS: Index of coronary microcirculatory resistance was measured in a hyperemic state induced by 7 experimental conditions in 21 pigs (IC bolus of papaverine (18 mg), ATP (40 µg, 80 µg, 160 µg, and 240 µg), and nicorandil (2 mg and 4 mg)). The 7 conditions were induced sequentially, and the average IMR was calculated. Because of the long-term hyperemic condition in the pilot experiments, the IMR was measured 1, 3, 5, 8, and 10 min after an IC bolus of alprostadil (10 µg) in another 7 pigs. RESULTS: The IMR induced by 240 µg of ATP or 4 mg of nicorandil was not significantly different from that induced by 18 mg of papaverine (both p > 0.05). A strong linear correlation was observed between IMRs with papaverine (18 mg) and nicorandil (4 mg) (R2 = 0.936, p < 0.001) and with papaverine (18 mg) and ATP (240 µg) (R2 = 0.838, p < 0.05). The IC bolus of nicorandil (4 mg) produced the smallest changes, whereas papaverine caused the most significant changes in mean blood pressure and heart rate (p < 0.05). Tachypnea and transient ST depression were more common with increasing ATP dosages (especially 240 µg). Alprostadil (5 min) yielded a significant hyperemic response but reduced baseline blood pressure by almost 40% for a long time. CONCLUSIONS: Intracoronary bolus administration of 4 mg of nicorandil was better than 18 mg of papaverine or 240 µg of ATP for induction of maximal hyperemia and IMR measurement in a pig model, whereas alprostadil was not suitable for IMR measurement.