Measuring dissolution profiles of single controlled-release drug pellets.

Many solid-dose oral drug products are engineered to release their active ingredients into the body at a certain rate. Techniques for measuring the dissolution or degradation of a drug product in vitro play a crucial role in predicting how a drug product will perform in vivo. However, existing techniques are often labor-intensive, time-consuming, irreproducible, require specialized analytical equipment, and provide only "snapshots" of drug dissolution every few minutes. These limitations make it difficult for pharmaceutical companies to obtain full dissolution profiles for drug products in a variety of different conditions, as recommended by the US Food and Drug Administration. Additionally, for drug dosage forms containing multiple controlled-release pellets, particles, beads, granules, etc. in a single capsule or tablet, measurements of the dissolution of the entire multi-particle capsule or tablet are incapable of detecting pellet-to-pellet variations in controlled release behavior. In this work, we demonstrate a simple and fully-automated technique for obtaining dissolution profiles from single controlled-release pellets. We accomplished this by inverting the drug dissolution problem: instead of measuring the increase in the concentration of drug compounds in the solution during dissolution (as is commonly done), we monitor the decrease in the buoyant mass of the solid controlled-release pellet as it dissolves. We weigh single controlled-release pellets in fluid using a vibrating tube sensor, a piece of glass tubing bent into a tuning-fork shape and filled with any desired fluid. An electronic circuit keeps the glass tube vibrating at its resonance frequency, which is inversely proportional to the mass of the tube and its contents. When a pellet flows through the tube, the resonance frequency briefly changes by an amount that is inversely proportional to the buoyant mass of the pellet. By passing the pellet back-and-forth through the vibrating tube sensor, we can monitor its mass as it degrades or dissolves, with high temporal resolution (measurements every few seconds) and mass resolution (700 nanogram resolution). As a proof-of-concept, we used this technique to measure the single-pellet dissolution profiles of several commercial controlled-release proton pump inhibitors in simulated stomach and intestinal contents, as well as comparing name-brand and generic formulations of the same drug. In each case, vibrating tube sensor data revealed significantly different dissolution profiles for the different drugs, and in some cases our method also revealed differences between different pellets from the same drug product. By measuring any controlled-release pellets, particles, beads, or granules in any physiologically-relevant environment in a fully-automated fashion, this method can augment and potentially replace current dissolution tests and support product development and quality assurance in the pharmaceutical industry.

Musical Instruments As Sensors.

The frequencies of notes made by a musical instrument are determined by the physical properties of the instrument. Consequently, by measuring the frequency of a note, one can infer information about the instrument's physical properties. In this work, we show that by modifying a musical instrument to contain a sample and analyzing the instrument's pitch, we can make precision measurements of the physical properties of the sample. We used the mbira, a 3000-year-old African musical instrument that consists of metal tines attached to a wooden board; these tines are plucked to play musical notes. By replacing the mbira's tines with bent steel tubing, filling the tubing with a sample, using a smartphone to record the sound while plucking the tubing, and measuring the frequency of the sound using a free software tool on our website, we can measure the density of the sample with a resolution of about 0.012 g/mL. Unlike existing tools for measuring density, the mbira sensor can be made and used by virtually anyone in the world. To demonstrate the mbira sensor's capabilities, we used it to successfully distinguish diethylene glycol and glycerol, two similar chemicals that are sometimes mistaken for each other in pharmaceutical manufacturing (leading to hundreds of deaths). We also show that consumers could use mbira sensors to detect counterfeit and adulterated medications (which represent around 10% of all medications in low- and middle-income countries). We expect that many other musical instruments can function as sensors and find important and lifesaving applications.

Sorting cells by their density.

Sorting cells by their type is an important capability in biological research and medical diagnostics. However, most cell sorting techniques rely on labels or tags, which may have limited availability and specificity. Sorting different cell types by their different physical properties is an attractive alternative to labels because all cells intrinsically have these physical properties. But some physical properties, like cell size, vary significantly from cell to cell within a cell type; this makes it difficult to identify and sort cells based on their sizes alone. In this work we continuously sort different cells types by their density, a physical property with much lower cell-to-cell variation within a cell type (and therefore greater potential to discriminate different cell types) than other physical properties. We accomplish this using a 3D-printed microfluidic chip containing a horizontal flowing micron-scale density gradient. As cells flow through the chip, Earth's gravity makes each cell move vertically to the point where the cell's density matches the surrounding fluid's density. When the horizontal channel then splits, cells with different densities are routed to different outlets. As a proof of concept, we use our density sorter chip to sort polymer microbeads by their material (polyethylene and polystyrene) and blood cells by their type (white blood cells and red blood cells). The chip enriches the fraction of white blood cells in a blood sample from 0.1% (in whole blood) to nearly 98% (in the output of the chip), a 1000x enrichment. Any researcher with access to a 3D printer can easily replicate our density sorter chip and use it in their own research using the design files provided as online Supporting Information. Additionally, researchers can simulate the performance of a density sorter chip in their own applications using the Python-based simulation software that accompanies this work. The simplicity, resolution, and throughput of this technique make it suitable for isolating even rare cell types in complex biological samples, in a wide variety of different research and clinical applications.

Measuring the mass, volume, and density of microgram-sized objects in fluid.

Measurements of an object's fundamental physical properties like mass, volume, and density can offer valuable insights into the composition and state of the object. However, many important biological samples reside in a liquid environment where it is difficult to accurately measure their physical properties. We show that by using a simple piece of glass tubing and some inexpensive off-the-shelf electronics, we can create a sensor that can measure the mass, volume, and density of microgram-sized biological samples in their native liquid environment. As a proof-of-concept, we use this sensor to measure mass changes in zebrafish embryos reacting to toxicant exposure, density changes in seeds undergoing rehydration and germination, and degradation rates of biomaterials used in medical implants. Since all objects have these physical properties, this sensor has immediate applications in a wide variety of different fields including developmental biology, toxicology, materials science, plant science, and many others.

Orientation-Based Control of Microfluidics.

Most microfluidic chips utilize off-chip hardware (syringe pumps, computer-controlled solenoid valves, pressure regulators, etc.) to control fluid flow on-chip. This expensive, bulky, and power-consuming hardware severely limits the utility of microfluidic instruments in resource-limited or point-of-care contexts, where the cost, size, and power consumption of the instrument must be limited. In this work, we present a technique for on-chip fluid control that requires no off-chip hardware. We accomplish this by using inert compounds to change the density of one fluid in the chip. If one fluid is made 2% more dense than a second fluid, when the fluids flow together under laminar flow the interface between the fluids quickly reorients to be orthogonal to Earth's gravitational force. If the channel containing the fluids then splits into two channels, the amount of each fluid flowing into each channel is precisely determined by the angle of the channels relative to gravity. Thus, any fluid can be routed in any direction and mixed in any desired ratio on-chip simply by holding the chip at a certain angle. This approach allows for sophisticated control of on-chip fluids with no off-chip control hardware, significantly reducing the cost of microfluidic instruments in point-of-care or resource-limited settings.

Antithrombotic efficacy of RPR208566, a novel factor Xa inhibitor, in a rat model of carotid artery thrombosis.

Coagulation factor Xa is the sole enzyme responsible for activating the zymogen prothrombin to thrombin, resulting in fibrin generation, platelet activation, and subsequent thrombus formation. Our objective was to evaluate the antithrombotic efficacy of the novel factor Xa inhibitor, 2-(3-carbamimidoyl-benzyl)-3-[(3', 4'dimethoxy-biphenyl-4-carbonyl)-amino]-butyric acid methyl ester-trifluoroacetate (RPR208566), in a well-established rat model of arterial thrombosis, and to compare the results with those obtained with argatroban and heparin, direct and indirect inhibitors of thrombin, respectively. Thrombus formation was initiated by placing a filter paper saturated with FeCl(2) on the adventia of the carotid artery for 10 min. Time-to-occlusion was measured from initiation of injury until blood flow reached zero. Formed thrombi were removed and weighed 60 min after the placement of the filter paper. RPR208566, heparin, and argatroban dose-dependently increased time-to-occlusion and reduced thrombus mass. When administered at 500 microgram/kg+50 microgram/kg/min, RPR208566 prolonged time-to-occlusion to 56+/-4 min (vs. 18+/-2 min for vehicle) and reduced thrombus mass to 3.0+/-0.7 mg (vs. 7.3+/-0.6 mg for vehicle). The highest doses of argatroban (500 microgram/kg+50 microgram/kg/min) and heparin (300 U/kg+10 U/kg/min) increased time-to-occlusion to the maximum of 60 min and decreased thrombus mass to 5.5+/-0.8 and 2.6+/-0.3, respectively. The antithrombotic effects of heparin and argatroban at these doses were associated with increases in activated partial thromboplastin time of 5.6+/-0.9- and 2.9+/-0.3-fold over baseline, respectively. However, the highest dose of RPR208566 produced a modest 1.3+/-0.1-fold increase in activated partial thromboplastin time. These results indicate that factor Xa inhibition with compounds such as RPR208566 may be an attractive mechanism for novel antithrombotic drug therapy.

Pharmacodynamic activity and antithrombotic efficacy of RPR120844, a novel inhibitor of coagulation factor Xa.

These studies were designed to examine the pharmacodynamic profile and antithrombotic efficacy of RPR120844, a competitive inhibitor of coagulation factor Xa, with a K(i) of 7 nM against human factor Xa. In vitro, RPR120844 doubled activated partial thromboplastin time (APTT) at concentrations of 1.54, 1.48, and 0.74 microM in plasma obtained from humans, dogs, and rats, respectively. Intravenous bolus administration of RPR 120844 at 0.3, 1, and 3 mg/kg to rats resulted in maximal increases in APTT of 1.8-, 2.6-, and 8.4-fold over baseline, respectively. The effect on prothrombin time (PT) was less pronounced, resulting in a 4.4-fold increase at 3 mg/kg. These effects were rapidly reversible; APTT and PT returned to control values by 30 min after dosing. Intragastric administration to rats at 50, 100, and 200 mg/kg resulted in modest increases in APTT and PT of 1.5- and 1.3-fold over baseline at the highest dose. Plasma levels were estimated by anti-Xa activity by using an amidolytic, chromogenic assay. Plasma levels were 0.65, 1.29, and 2.45 microM at 30 min after dosing at 50, 100, and 200 mg/kg, respectively. Intravenous administration to dogs at 0.1 and 0.3 mg/kg produced maximal increases in APTT of 1.7- and 2.4-fold over baseline, respectively. Intragastric administration to dogs at 50 mg/kg resulted in maximal increases in APTT and PT of 1.7- and 1.1-fold over baseline, with peak plasma levels of 3.9 microM observed at 15 min after dosing. In a rat model of FeCl2-induced carotid artery thrombosis, RPR120844 (3 mg/kg, i.v. bolus + 300 microg/kg/min constant infusion; n = 4) significantly increased time-to-occlusion from 18+/-1 min (vehicle, n = 4) to 60 min (maximal observation time) and reduced thrombus mass from 5.5 +/- 0.2 mg (vehicle) to 1.4 +/- 0.2 mg. These results indicate that RPR120844 is a potent, selective inhibitor of Xa that exhibits oral activity and is efficacious in a standard model of arterial thrombosis.

Sulfonamidopyrrolidinone factor Xa inhibitors: potency and selectivity enhancements via P-1 and P-4 optimization.

Sulfonamidopyrrolidinones were previously disclosed as a selective class of factor Xa (fXa) inhibitors, culminating in the identification of RPR120844 as a potent member with efficacy in vivo. Recognizing the usefulness of the central pyrrolidinone template for the presentation of ligands to the S-1 and S-4 subsites of fXa, studies to optimize the P-1 and P-4 groups were initiated. Sulfonamidopyrrolidinones containing 4-hydroxy- and 4-aminobenzamidines were discovered to be effective inhibitors of fXa. X-ray crystallographic experiments in trypsin and molecular modeling studies suggest that our inhibitors bind by insertion of the 4-hydroxybenzamidine moiety into the S-1 subsite of the fXa active site. Of the P-4 groups examined, the pyridylthienyl sulfonamides were found to confer excellent potency and selectivity especially in combination with 4-hydroxybenzamidine. Compound 20b (RPR130737) was shown to be a potent fXa inhibitor (K(i) = 2 nM) with selectivity against structurally related serine proteinases (>1000 times). Preliminary biological evaluation demonstrates the effectiveness of this inhibitor in common assays of thrombosis in vitro (e.g. activated partial thromboplastin time) and in vivo (e.g. rat FeCl(2)-induced carotid artery thrombosis model).

Identification and initial structure-activity relationships of a novel class of nonpeptide inhibitors of blood coagulation factor Xa.

The discovery and some of the basic structure-activity relationships of a series of novel nonpeptide inhibitors of blood coagulation Factor Xa is described. These inhibitors are functionalized beta-alanines, exemplified by 2a. Docking experiments placing 2a in the active site of Factor Xa implied that the most expeditious route to enhancing in vitro potency was to modify the group occupying the S3 site of the enzyme. Increasing the hydrophobic contacts between the inhibitor and the enzyme in this region led to 8, which has served as the prototype for this series. In addition, an enantioselective synthesis of these substituted beta-alanines was also developed.

Low-molecular-weight heparin (fragmin) and thrombin active-site inhibitor (argatroban) compared in experimental arterial and venous thrombosis and bleeding time.

The antithrombotic and bleeding effects of a low-molecular-weight heparin (LMWH, fragmin) and a thrombin active-site inhibitor (argatroban) were determined in anesthetized rats. Occlusive thrombi were produced in the vena cava, either by partial stasis of blood flow or transmural vessel injury, and in the carotid artery by transmural vessel injury. Bleeding time was measured by puncturing small mesenteric arteries. Each drug was tested in multiple intravenous (i.v.) doses and inhibited venous and arterial thrombosis when the activated partial thromboplastin time (APTT) was increased as much as or more than twofold, although greater APTT increases were required with fragmin and against arterial thrombosis. Fragmin and argatroban decreased to an equivalent extent the weight of venous thrombi induced by stasis (> or = 99%) or vessel injury (90 and 96%, respectively). The maximum inhibition of arterial thrombosis was less with fragmin (69%) and argatroban (65%) and required higher doses of each drug relative to venous thrombosis. At doses that were just optimal against arterial thrombosis, bleeding time was increased moderately by fragmin (32%) and was unaffected by argatroban. These studies demonstrate that doses of fragmin and argatroban that exert comparable antithrombotic activity in large arteries and veins have only moderate effects on bleeding time in small arteries.

Sensitivity of experimental venous and arterial thrombosis and bleeding to ancrod-induced defibrinogenation.

The effect of ancrod-induced defibrinogenation on thrombosis and bleeding time was determined in anesthetized rats. Functional plasma fibrinogen levels were reduced 42, 71, 94 and 93% by ancrod doses of 5, 10, 20 and 30 U/kg, respectively, while a 2.5 U/kg dose was without significant effect. Ancrod inhibited vena cava thrombosis induced by partial stasis of blood flow combined with mild vascular injury. Thrombus weight was decreased 85 and 93% by the 10 and 20 U/kg doses, but was unaffected at lower doses. In contrast, ancrod doses of up to 30 U/kg did not significantly decrease carotid artery thrombi formed in response to oxidative transmural vessel injury. Ancrod caused a dose-dependent increase in bleeding time measured by puncturing small mesenteric arteries with a hypodermic needle. The bleeding time increase was approximately 38% in response to the 2.5 and 5 U/kg doses, and 182% in response to the 10 U/kg dose. These studies demonstrate that ancrod-induced reductions in plasma fibrinogen more effectively inhibit venous compared to arterial thrombosis, although these activities require doses that also increase bleeding time in small arteries.

Comparison of thrombin active site and exosite inhibitors and heparin in experimental models of arterial and venous thrombosis and bleeding.

Different pharmacological approaches to thrombin inhibition were compared for their effects on thrombosis and bleeding time in anesthetized rats. Thrombosis was induced in the carotid artery by transmural vessel injury and in the vena cava by partial blood flow stasis combined with mild endothelial disruption. Small mesenteric arteries were punctured with a hypodermic needle to measure the bleeding time. Dose-response relationships were determined with a thrombin active site inhibitor, N-methyl (GYKI 14,766); a thrombin exosite inhibitor, succinyl-Phe-Glu-Pro-Ile-Pro-Glu-Glu-Tyr-cyclohexylalanine-Gln (BMS 180,742); and heparin. BMS 180,742 interferes with fibrinogen binding to the thrombin exosite but, unlike GYKI 14,766, it does not block thrombin's catalytic site. The effects on thrombosis and bleeding time were correlated with ex vivo clotting times using the activated partial thromboplastin time for heparin and the thrombin time for GYKI 14,766 and BMS 180,742. Venous thrombosis was inhibited more than 90% by all three inhibitors at doses that either produced threshold increases or had no effect on bleeding and clotting times. Arterial thrombosis was inhibited 82% by GYKI 14,766 and 63% by heparin but it was not inhibited by BMS 180,742. These antithrombotic activities were accompanied by a maximal activated partial thromboplastin time increase and doubling of the bleeding time with heparin and a maximal thrombin time prolongation and 35% increase in bleeding time with GYKI 14,766. These results suggest that thrombin inhibitors, which act at the active site or exosite or through antithrombin III, are equally efficacious against venous thrombosis but active site inhibitors are the most effective against arterial thrombosis.

Superior activity of a thromboxane receptor antagonist as compared with aspirin in rat models of arterial and venous thrombosis.

We determined the effects of aspirin and a novel thromboxane A2/prostaglandin endoperoxide (TP)-receptor antagonist, BMS-180291, on thrombosis and bleeding times in skin and mesenteric arteries. In anesthetized rats, occlusive thrombosis was induced in the carotid artery by topical application of ferrous chloride and in the vena cava by blood flow stasis combined with either infusion of thromboplastin or hypotonic saline. Aspirin (1, 10, and 50 mg/kg) did not reduce arterial or venous thrombus weight significantly. BMS 180,291 (150 micrograms/kg/min) decreased arterial thrombus weight and hypotonic saline-induced caval thrombus weight by 58 and 57%, respectively. BMS-180291 lacked antithrombotic activity at a lower dose (50 micrograms/kg/min) and failed to inhibit thromboplastin-induced caval thrombosis. BMS-180291 (150 micrograms/kg/min) significantly reduced arterial thrombus weight by 40% when plasma epinephrine concentration was increased to 5 ng/ml. BMS-180291 and aspirin produced increases of only < or = 30% in bleeding times. These results demonstrate that BMS-180291 has antithrombotic activity in experimental aspirin-resistant arterial and venous thrombosis. Both aspirin and BMS-180291 have only modest effects on small artery hemostasis in rats.

Comparison of a thromboxane receptor antagonist and aspirin in experimental arterial thrombosis.

The antithrombotic activities of aspirin, the thromboxane (Tx) A2/prostaglandin endoperoxide-receptor (TP-receptor) antagonist, SQ 30,741, and heparin were determined in anesthetized rats. Heparin (3 doses of 50, 300 U/kg), aspirin (1 and 10 mg/kg), SQ 30,741 (1 mg/kg + 1 mg/kg/h), or the combination of SQ 30,741 and aspirin (10 mg/kg) was administered intravenously before inducing occlusive thrombosis with 0.1-mA stimulation of the intimal surface of the carotid artery. Light and electron microscopy revealed the thrombi to be composed predominantly of platelets enmeshed in a fibrin network. Heparin (300 U/kg), SQ 30,741 and SQ 30,741 + aspirin decreased average thrombus weight by 54, 57 and 39%, respectively. These treatments also reduced the incidence of occlusion and improved carotid blood flow during thrombosis. In contrast, aspirin alone (1 and 10 mg/kg) and the lower heparin dose (50 U/kg) did not significantly affect thrombus weight or carotid blood flow. To verify adequate drug dosage, pharmacological activities were characterized ex vivo in separate rats. Aspirin (10 mg/kg) inhibited maximum thromboxane (Tx) B2 production in whole blood by 99 +/- 1% and SQ 30,741 blocked 96% of platelet TP-receptors. Heparin increased the activated partial thromboplastin time (APTT) partially at 50 U/kg (approximately 3-fold) and maximally at 300 U/kg (> 10-fold). These experiments demonstrate the contribution of platelet and coagulation mechanisms to a thrombosis model which is sensitive to a TP-receptor antagonist, but not aspirin.

Effects of antithrombotic drugs in a rat model of aspirin-insensitive arterial thrombosis.

These studies describe experimental conditions where aspirin is less effective than other antiplatelet and anticoagulant drugs in inhibiting acute arterial thrombosis. External electrolytic injury of the rat carotid artery was used to induce occlusive thrombi in 97% of vehicle-treated rats. Thrombi were revealed by light and electron microscopy to be comprised primarily of platelets enmeshed in a fibrin network. The thrombin inhibitor D-phenylalanyl-L-prolyl-L-arginyl chloromethylketone (PPACK; 6 mg/kg, i.v.) decreased thrombus weight by 90%. Aspirin alone (1, 10 and 30 mg/kg, i.v.), dipyridamole alone (5 mg/kg i.v.) and aspirin (1 and 10 mg/kg, i.v.) in combination with dipyridamole (5 mg/kg, i.v.) did not inhibit thrombosis. The platelet-activating factor (PAF) antagonist, WEB 2086, (1 mg/kg i.v.) was also ineffective. Other drugs had intermediate activity. Thrombi were decreased 56% by the thromboxane receptor antagonist, BMS 180,291, either alone (5.8 mg/kg i.v.) or in combination with aspirin (10 mg/kg, i.v.). Heparin (900 U/kg, i.v.), warfarin (0.25 mg/kg, p.o. once daily for 3 days) and ticlopidine (200 mg/kg, p.o. once daily for 3 days) reduced thrombus weight by 63, 73 and 43% respectively. Reductions in thrombus weight were always associated with improvements in either average blood flow or vessel patency.

Thrombin inhibition compared with other antithrombotic drugs in rats.

An aspirin-sensitive model of arterial thrombosis suitable for rapid evaluation of antithrombotic drugs was developed and characterized in anesthetized rats. Carotid artery thrombi were formed in response to electrical stimulation and were occlusive in 84% of vehicle-treated rats. Light and electron microscopy revealed these thrombi to be platelet-rich and fibrin-rich masses adherent to the injured vessel wall. Intravenous administration of aspirin (10 mg/kg), heparin (300 U/kg), a thromboxane (Tx) A2-receptor antagonist (SQ 29,548, 0.2 mg/kg + 0.2 mg/kg/hr), or the thrombin inhibitor D-phenyl alanyl-L-prolyl-L-arginyl chloromethyl ketone (PPACK, 52 micrograms/kg/min) decreased average thrombus weight by 35, 50, 57 and 94%, respectively. Each of these drugs also reduced the frequency of occlusion to < 25%. In contrast, thrombus weight and vessel occlusion were not decreased by a serotonin antagonist (ketanserin, 0.3 mg/kg, i.v.), or after 14 days of oral dosing with either the calcium antagonist diltiazem (60 mg/kg) or SQ 33,351 (30 mg/kg).

Activity of the short-acting thromboxane receptor antagonist, SQ 30,741, in thrombolytic and vasospastic models in monkeys.

The effects of the thromboxane receptor antagonist SQ 30,741 (1 mg/kg) on reflow after thrombolysis and on vasoconstrictor responses to the thromboxane agonist U-46,619 was determined in cynomolgus monkeys. SQ 30,741 (n = 5) or vehicle (n = 4) was administered to anesthetized monkeys upon reocclusion of a stenotic and electrically injured carotid artery, which had been recanalized successfully with streptokinase and heparin. Once blood flow again decreased to zero the treatment was repeated. SQ 30,741 significantly (P less than .05) enhanced reflow by 113% after the first administration and by 150% after the second administration. The respective times to each reocclusion were greater after SQ30,741 (49 +/- 9 and 61 +/- 23 min; P less than .01 and P less than .05) than with vehicle (10 +/- 3 and 15 +/- 2 min). The potency of SQ 30,741 was demonstrated in other anesthetized monkeys by a 8.5 +/- 1.1-fold (n = 3) shift to the right in the U-46,619 dose-response for renal vasoconstriction. The effect of SQ 30,741 (n = 5) on pre-existing renal vasoconstriction was determined using conscious monkeys in which an individually tailored dose of U-46,619 was chosen to sustain an average 82% reduction in blood flow. An arterial injection of SQ 30,741 rapidly returned flow to base-line values, but this antagonism was limited in duration, and flow again reached the nadir within 46 +/- 7 min of continuous U-46,619 infusion. The abbreviated duration of the biological activity of SQ 30,741 in vivo was consistent with its short plasma T1/2 (9.5 +/- 1.3 min; n = 3) determined in separate unanesthetized monkeys by a radioreceptor assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Protamine-induced pulmonary hypertension in heparinized monkeys and pigs is inhibited by the thromboxane receptor antagonist SQ 30,741.

When protamine reverses heparin anticoagulation a small fraction of patients develops pulmonary hypertension. This response is variably expressed in other species and thromboxane may be one of its mediators. We have compared the pulmonary vascular responses of pigs and monkeys to protamine (3 mg/kg, i.v.) administered 15 min after heparin (300 U/kg, i.v.). The role of thromboxane A2/prostaglandin H2 (TxA2/PGH2)-receptor activation in this response was investigated with the selective TxA2/PGH2-receptor antagonist, SQ 30,741, at a dose (1 mg/kg, i.v.) shown to inhibit U-46,619-induced pulmonary vasoconstriction by greater than or equal to 99%. SQ 30,741 or vehicle (1.5 ml saline) was given 2 min before protamine in Yucatan minipigs (n = 6-7) and African green monkeys (n = 8-9). In saline-treated monkeys and pigs, protamine increased pulmonary vascular resistance (131 +/- 46 and 478 +/- 18%, respectively) primarily by increasing pulmonary artery pressures (54 +/- 19 and 166 +/- 42%, respectively). In pigs only, pulmonary artery flow was also reduced by 33 +/- 9%. These responses peaked within 1 to 3 min and returned to baseline in approximately 5 (monkey) and approximately 15 (pig) min. In monkeys and pigs pretreated with SQ 30,741 the increases in pulmonary vascular resistance (17 +/- 4 and 16 +/- 9%, respectively, p less than 0.05) and pulmonary artery pressure (10 +/- 3 and 16 +/- 9%, respectively, p less than 0.05) were significantly inhibited. SQ 30,741 also accelerated reversal of established hypertension in pigs when given 1 min after protamine. However, transient reductions in circulating monkey leukocytes (approximately 70%) and platelets (approximately 16%) were unaffected by SQ 30,741.(ABSTRACT TRUNCATED AT 250 WORDS)

Leukotrienes cause mesenteric vasoconstriction and hemoconcentration in rats without activating thromboxane receptors.

Thromboxane A2/prostaglandin H2 (TP)-receptor activation has been reported to participate in some of the responses to peptide leukotrienes (LT). We examined the effect of TP-receptor antagonism on LT-induced mesenteric vasoconstriction and hemoconcentration in anesthetized rats. The antagonist used in these studies, SQ 30,741, was shown to have high selectivity and potency for vascular TP-receptors in the rat. Arterial (i.a.) injection of LTC4 and D4 elicited dose-dependent and transient reductions in mesenteric blood flow without changes in arterial blood pressure. These responses were unaffected by a dose of SQ 30,741 which produced approximately 99% inhibition of similar responses to U-46,619. In contrast, LT-induced mesenteric vasoconstriction was inhibited approximately 90% by two LT antagonists, LY 171,883 and SKF 104,353. In other experiments i.v. infusion of LTD4 caused increases in hematocrit and reductions in arterial blood pressure that were not influenced by SQ 30,741. These data suggest that increases in mesenteric vascular resistance and hemoconcentration in response to LTs are not the result of TP-receptor activation.

Effect of thromboxane antagonism on recanalization during streptokinase-induced thrombolysis in anesthetized monkeys.

The effect of a selective thromboxane A2 (TxA2) receptor antagonist, SQ 30,741, on streptokinase-induced thrombolysis was examined in pentobarbital-anesthetized cynomolgus monkeys. The intimal surface of a stenosed carotid artery was stimulated with 100 microA anodal current to produce an occlusive thrombus. After 45 min of zero blood flow, a 1-h intraarterial (i.a.) infusion of streptokinase (680 U/min) was injected proximal to the thrombus. Five minutes before streptokinase (SK) intravenous (i.v.) infusions of heparin (200 U/kg + 120 U/h) and either SQ 30,741 (2 mg/kg + 2 mg/kg/min, n = 8) or vehicle (1 ml/h saline, n = 7) were started and maintained for 3 h. In four monkeys not given streptokinase or heparin, no recanalization was detected and occlusive thrombi were observed after 3 h. All animals receiving streptokinase were recanalized. SQ 30,741 had no effect on return of flow during streptokinase infusion, but increased average reflows during the second (60%, p less than 0.05) and third hours (159%, p less than 0.01). Average blood flows were decreased from the second to third hours with vehicle (p less than 0.001) and remained stable with SQ 30,741. Thromboxane antagonism also increased minimal blood flows during the third hour (438%, p less than 0.01) and decreased the total time reoccluded by 73% (p less than 0.05). However, SQ 30,741 had no effect on the time to recanalization, the maximum reflow, and both number of animals reoccluded and average number of reocclusions. Fibrinogen levels were equivalently diminished (8%, p less than 0.05), and platelet counts were unaffected in both treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)