Iliac Blood Flow Research Articles

Intra-aortic balloon pump synchronized with chest compressions improves outcome during cardiopulmonary resuscitation in experimental cardiac arrest

BackgroundIntra-aortic balloon pump (IABP) and resuscitative endovascular balloon occlusion of the aorta (REBOA) are two endovascular intervention methods for circulatory support. The aim of this study was to compare the hemodynamic effects of simultaneous mechanical chest compressions (MCC) with IABP, REBOA and those with only MCC (overall and detailed in the MCC cycle) and return of spontaneous circulation (ROSC) during cardiopulmonary resuscitation (CPR) in experimental non-traumatic cardiac arrests (CA). MethodCA was electrically induced (ventricular fibrillation) in 24 anesthetized pigs, which then were randomized to MCC synchronized IABP (n = 8), total occluded REBOA (n = 8), or control (n = 8). After 10 min of CA, CPR with MCC was started followed by one of the interventions after one minute of CPR. Every other minute after MCC start, the pigs were defibrillated with 200 J if VF/ventricular tachycardia, and after six minutes, adrenaline was administered and repeated every four minutes. The proportions of ROSC were calculated. Hemodynamic variables, including systemic blood and coronary perfusion pressures (CPP), and carotid and iliac blood flows, were collected and analyzed with 0.02 s resolution. ResultsIn both the IABP and REBOA groups, 7 of 8 animals (87.5 %) achieved ROSC, in contrast with 2 of 8 (25 %) in the control group (P = 0.04). IABP and REBOA significantly increased systemic arterial pressure (P = 0.002 and P = 0.015, respectively), and REBOA also increased CPP and carotid blood flow when compared to controls (P = 0.007 and P = 0.03, respectively). Animals with IABP had a preserved blood flow in the iliac artery during CPR. No differences were detected after ROSC in hemodynamic, metabolic, and organ injury variables between the REBOA and IABP groups. ConclusionBoth IABP and REBOA increased the proportion of ROSC compared to controls. However, REBOA occluded distal blood flow, while IABP maintained it. This study suggests that MCC synchronized IABP could be an adjunct in the treatment of non-traumatic CA.

Invivo evaluation of a new hybrid graft using retrograde visceral perfusion for thoracoabdominal aortic repair in an animal model.

ObjectivesThe SPIDER technique for hybrid thoracoabdominal aortic aneurysm repair can avoid thoracotomy and extracorporeal circulation. To improve technical feasibility and safety, the new Thoracoflo graft, consisting of a proximal stent graft connected to a 7-branched abdominal prosthesis, was evaluated in a pig model for technical feasibility testing, before implantation in humans.MethodsRetroperitoneal exposure of the infradiaphragmatic aorta, including visceral and renal arteries, was performed in 7 pigs (75-85 kg). One iliac branch was temporarily attached to the distal aorta to maintain retrograde visceral and antegrade iliac perfusion after deployment of the thoracic stent graft segment (SPIDER technique). The proximal stent-grafted segment was deployed in the thoracic aorta via direct aortic puncture over the wire without fluoroscopy. The graft was deaired before flow via the iliac side branch to the visceral and iliac arteries was established. Visceral, renal, and lumbar arteries were subsequently sutured to the corresponding side branches of the graft. Technical feasibility, operating and clamping time, blood flow, and tissue perfusion in the related organs were evaluated before implantation and after 3 and 6 hours using transit-time flow measurement and fluorescent microspheres. Final angiography or postprocedural computed tomography angiography were performed.ResultsOver-the-wire graft deployment was successful in 6 animals without hemodynamic alteration (P = n.s.). In 1 pig, the proximal stent graft section migrated as the guidewire was not removed, as recommended, before release of the proximal fixation wire. Angiography and computed tomography scan confirmed successful graft implantation and transit-time flow measurement confirmed good visceral and iliac blood flow. Fluorescent microspheres confirmed good spinal cord perfusion.ConclusionsOver-the-wire implantation of the Thoracoflo graft using the SPIDER technique is feasible in a pig model. No fluoroscopy was required. For safe implantation, it is mandatory to follow the single steps of implantation.

Sandwich EVAR is Salvageable Technique in Juxtarenal AAA

The most common technical concern in Endovascular Aneurysm Repair (EVAR) is the proximal landing zone of stent. Sandwich technique is the effective procedure to preserve internal iliac blood flow. This case report describes using this procedure for successful EVAR in patient with juxtarenal abdominal aortic aneurysm.

Preparation of Peptide and Recombinant Tissue Plasminogen Activator Conjugated Poly(Lactic-Co-Glycolic Acid) (PLGA) Magnetic Nanoparticles for Dual Targeted Thrombolytic Therapy.

Recombinant tissue plasminogen activator (rtPA) is the only thrombolytic agent that has been approved by the FDA for treatment of ischemic stroke. However, a high dose intravenous infusion is required to maintain effective drug concentration, owing to the short half-life of the thrombolytic drug, whereas a momentous limitation is the risk of bleeding. We envision a dual targeted strategy for rtPA delivery will be feasible to minimize the required dose of rtPA for treatment. For this purpose, rtPA and fibrin-avid peptide were co-immobilized to poly(lactic-co-glycolic acid) (PLGA) magnetic nanoparticles (PMNP) to prepare peptide/rtPA conjugated PMNPs (pPMNP-rtPA). During preparation, PMNP was first surface modified with avidin, which could interact with biotin. This is followed by binding PMNP-avidin with biotin-PEG-rtPA (or biotin-PEG-peptide), which was prepared beforehand by binding rtPA (or peptide) to biotin-PEG-maleimide while using click chemistry between maleimide and the single –SH group in rtPA (or peptide). The physicochemical property characterization indicated the successful preparation of the magnetic nanoparticles with full retention of rtPA fibrinolysis activity, while biological response studies underlined the high biocompatibility of all magnetic nanoparticles from cytotoxicity and hemolysis assays in vitro. The magnetic guidance and fibrin binding effects were also confirmed, which led to a higher thrombolysis rate in vitro using PMNP-rtPA or pPMNP-rtPA when compared to free rtPA after static or dynamic incubation with blood clots. Using pressure-dependent clot lysis model in a flow system, dual targeted pPMNP-rtPA could reduce the clot lysis time for reperfusion by 40% when compared to free rtPA at the same drug dosage. From in vivo targeted thrombolysis in a rat embolic model, pPMNP-rtPA was used at 20% of free rtPA dosage to restore the iliac blood flow in vascular thrombus that was created by injecting a blood clot to the hind limb area.

Endovascular treatment of hypogastric artery aneurysms

ObjectiveInternal iliac artery aneurysm (IIAA) is a rare entity. Its treatment can be technically challenging. The aim of this study was to evaluate the treatment possibilities in an era of advanced endovascular techniques and their potential to preserve iliac blood flow while reliably excluding the aneurysm. MethodsA retrospective analysis of 46 consecutive patients with endovascularly treated IIAA was performed. Data were collected from a single-institution aortoiliac database. The following end points were recorded: technique of aneurysm exclusion, technical success rates, perioperative morbidity and mortality, primary patency, and midterm follow-up. ResultsBetween September 2009 and May 2016, a total of 46 patients with 55 IIAAs were identified. The majority of patients (n = 39 [84.8%]) had aortoiliac aneurysms and seven had isolated IIAAs (15.2%). The following surgical techniques were used: implantation of iliac branch devices (IBDs; n = 29), occlusion of the internal iliac artery (IIA) by ostium coverage with or without prior coil embolization (n = 23), and other endovascular techniques (n = 3). Primary assisted technical success was achieved in 93.1% of IBD implantations and in 100% of occlusions by ostium coverage and other techniques. Overall 30-day mortality was 4.3% (n = 2) and 0% in electively treated patients. Assisted midterm patency after IBD implantation was 93.1%. Gluteal claudication occurred in seven patients (15.2%) who had undergone intentional or accidental occlusion of the IIA or the superior gluteal artery. Reintervention rates within the midterm follow-up were 13.8% (n = 4) after IBD implantation and 4.3% (n = 1) after coverage of the IIA ostium. No ruptures were observed during follow-up, and no complications occurred during reinterventions. ConclusionsImplantation of IBD devices for the treatment of hypogastric artery aneurysms shows good technical results with a high primary patency and a low rate of perioperative complications. Although successful aneurysm exclusion while preserving pelvic blood flow is associated with a higher rate of reinterventions during midterm follow-up, it should be taken into consideration, especially in complex endovascular aortoiliac aneurysm repair.

Thrombolysis induced by intravenous administration of plasminogen activator in magnetoliposomes: dual targeting by magnetic and thermal manipulation

In previously published studies, intra-arterial (i.a.), but not intravenous (i.v.) delivery of recombinant tissue-type plasminogen activator (rtPA) immobilized on the surface of magnetic nanoparticles induces thrombolysis by magnetic targeting. We asked whether i.v. delivery of protected rtPA in a thermosensitive magnetoliposome (TML@rtPA) may achieve target thrombolysis. PEGylated TML@rtPA was optimized and characterized; controlled release of rtPA was achieved by thermodynamic and magnetic manipulation in vitro. The lysis index of TML@rtPA incubated with blood at 43 °C vs. 37 °C was 53 ± 11% vs. 81 ± 3% in thromboelastograms, suggesting thermosensitive thrombolysis of TML@rtPA. In a rat embolic model with superfusion of 43 °C saline on a focal spot on the iliac artery with clot lodging, release of rtPA equivalent to 20% regular dose from TML@rtPA administered i.a. vs. i.v. significantly restored iliac blood flow 15 vs. 55 min after clot lodging, respectively. TML@rtPA with magnetic guiding and focal hyperthermia may be potentially amendable to target thrombolysis.

Clinical study on the different lengths of inferior vena cava stent implantation for non-thrombotic iliac vein lesions

Objective To assess the safety and influence of the stents extended into inferior vena cava in patients with non-thrombotic iliac vein lesions (NIVLs) on the bilateral iliac vein blood flow. Methods We retrospectively reviewed data from July 2008 to June 2017 in 197 patients with NIVLs who underwent iliac vein stenting and complete follow-up was obtained at our institution.Of these patients, stents extended into IVC more than 10 mm in 141 cases, less than 5 mm in 22 cases, and 34 cases were between 5 and 10 mm.Restenosis and thrombosis of bilateral iliac vein and patency of these stents were assessed in the follow-up.The count data were expressed by percentage (%), and the sample comparison rate was analyzed by Fisher exact test formula.The measurement data were first tested for normal distribution and homogeneity of variance, and then corrected t test. Results The two hundred and five iliac vein stents were placed in 197 patients. During a mean follow-up of 58.7 months (6 to 98 months), there were no thrombosis occurred in the contralateral iliac vein, 6 patients suffered restenosis or new thrombosis in the stents, the incidence between stenting positions less than 5 mm (13.6%, 3/22) and those more than 5 mm (3.43%, 6/175) was sighificantly different (P<0.001), and 5 of 6 patients had a good patency after endovascular therapy. During the fllow-up, the primary and assisted-primary patency rates were 97.0% and 99.5%. Conclusions From these data, it appears that there is a very high patency rates of the stenting treatment for the NIVLs, and it is safe for the stents extended into the IVC, stenting across the iliocaval confluence can result in a small number of new contralateral thromboses. Moreover, the risk of stents restenosis or occlusion is high when stents are not extended into IVC. Key words: Iliac vein; Stent; Vein thrombosis; Interventional therapy

P13.06: Ultrasound evaluation of saftly of postpartum hemorrhage (PPH) compression belt in reduction of uterine, internal iliac and femoral artery blood flow in healthy postpartum women

P13.06: Ultrasound evaluation of saftly of postpartum hemorrhage (PPH) compression belt in reduction of uterine, internal iliac and femoral artery blood flow in healthy postpartum women

Different blood pressure responses to opioids in 3 rat hypertension models: role of the baseline status of sympathetic and renin-angiotensin systems.

Opioids interact with sympathetic and renin-angiotensin systems in control of mean arterial pressure (MAP). Our earlier finding that biphalin, a synthetic enkephalin analogue, decreased MAP in anaesthetized spontaneously hypertensive rats (SHR) prompted us to further explore this action, to get new insights into pathogenesis of various forms of hypertension. Biphalin effects were studied in SHR, uninephrectomized rats on a high-salt diet (HS/UNX), and rats with angiotensin-induced hypertension (Ang-iH). Besides MAP, renal and iliac blood flows (RBF, IBF) and vascular resistances were measured. In anaesthetized and conscious SHR, biphalin (300 μg·h-1·kg-1 i.v.) decreased MAP by ∼10 and ∼20 mm Hg, respectively (P < 0.001). In anaesthetized HS/UNX and normotensive rats, MAP increased by ∼6-7 mm Hg (P < 0.02); without anaesthesia, only transient decreases occurred. MAP never changed in Ang-iH rats. Morphine (1.5 mg·h-1·kg-1 i.v.) decreased MAP in HS/UNX but only transiently so without anaesthesia; such anaesthesia dependence of response was also seen in normotensive rats. Ang-iH rats never responded to morphine. Hypotensive effect in SHR only depends primarily on the reduction by biphalin of vascular responsiveness to increased sympathetic stimulation; such increase is well documented for SHR. No MAP response to biphalin or morphine in Ang-iH could depend on angiotensin-induced alterations of the vascular wall morphology and function.

38 Development of a rabbit iliac model for testing the bio-neutrality of novel coronary stents and scaffolds

Introduction We developed a rabbit iliac model to investigate the in vivo interaction of coronary stents with the vessel wall and circulating blood. A recovery model was used to assess the biocompatibility of RGD coated stents. Methods The stent thrombosis model consisted of male NZW rabbits medicated with Aspirin and Clopidogrel 1mg/kg, following platelet function studies to test appropriate antiplatelet response. Platelets were fluorescently labelled ex-vivo and re-injected pre-operatively. Superficial femoral (SFA) and iliac arteries were exposed bilaterally. An angioplasty balloon catheter introduced via a femoral arteriotomy was used to injure the proximal common iliac artery. A stent was deployed at the site of injury and the SFA ligated to reduce flow. Contralateral procedures allowed testing of study and control stents. Iliac blood flow was measured bilaterally for 2 h post stenting and following euthanasia, stented vessels removed and fixed. Platelet deposition on both stents was compared using immunofluorescence and explanted vessels were imaged with OCT. The recovery model involved limited dissection. After 28 days, the stented vessels were perfusion fixed, explanted and sent to CVPath for processing. Results We performed 15 acute, including 6 BVS vs durable polymer stents and 13 recovery procedures, including 10 RGD coated vs BMS. Differences in flow, platelet deposition and OCT will be presented. Conclusions The rabbit iliac model has proven to be a reproducible method to assess the acute thrombogenicity and chronic biocompatibility of coronary stents and scaffolds.

Magnetically controlled release of recombinant tissue plasminogen activator from chitosan nanocomposites for targeted thrombolysis.

Ionic cross-linking of water-soluble chitosan with sodium tripolyphosphate in the presence of recombinant tissue plasminogen activator (rtPA) and magnetite (Fe3O4) nanoparticles could produce rtPA-encapsulated magnetic chitosan nanoparticles (MCNPs-rtPA). MCNPs do not elicit cytotoxicity and hemolysis in vitro. MCNPs-rtPA showed a negligible release of the rtPA protein when stored in phosphate buffer for 28 days. In contrast, the burst release of rtPA from MCNPs-rtPA was found in the serum with 60% of the original activity released in 30 min. The drug release into the serum is also magnet-sensitive; the release could be turned down with a magnetic field when MCNPs-rtPA was pelleted and reversibly turned on after removing the magnetic field when MCNPs-rtPA was dispersed. An in vitro thrombolytic study by thromboelastometry indicated a controlled release of rtPA from MCNPs-rtPA. In a rat embolic model where a preformed blood clot lodged in the left iliac artery upstream of the pudic epigastric branch, MCNPs-rtPA (0.2 mg kg-1 rtPA) was administered and guided magnetically to the clot, followed by mobile magnetic guidance for 60 min. Iliac blood flow increased immediately in response to the treatment, and reached a stable level ∼50 min after drug administration and the hind limb perfusion rate was restored from 53% to 75% of the basal level. Effective thrombolysis was therefore successfully demonstrated at an rtPA dose equivalent to 20% of the regular dose when the MCNPs-rtPA pellet was magnet-guided to the blood clot, followed by a triggered release of rtPA when switched to mobile magnetic guidance.

An antihypertensive opioid: Biphalin, a synthetic non-addictive enkephalin analog decreases blood pressure in spontaneously hypertensive rats.

Endogenous opioid systems may be engaged in the control of arterial pressure (MAP), however, given the risk of addiction, opioid receptor agonists are not used in antihypertensive therapy. We examined cardiovascular effects of biphalin, a potentially non-addictive dimeric enkephalin analog, an agonist of opioid μ and δ receptors. Biphalin was infused iv at 150μg/kg/h to anesthetized spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Along with MAP and heart rate (HR), renal blood flow (RBF) and iliac blood flow (IBF, a measure of hind limb perfusion) were measured using Transonic probes on renal and iliac artery, respectively. The effects of biphalin were compared with those of intravenous morphine (1.5mg/kg/h). In two SHR groups biphalin decreased MAP from 143±2 to 130±2 and from 177±4 to 167±3mmHg (p<0.001) while HR did not change or modestly decreased. The renal blood flow (RBF) increased modestly and both renal and hind limb vascular resistances decreased significantly (p<0.001). The responses were blocked by inhibition of peripheral opioid receptors with naloxone methiodide. Unlike in SHR, in WKY rats biphalin did not change MAP or vascular resistances. Morphine infusion decreased MAP in SHR from 169±6 to 150±6mmHg (less decrease in WKY) and significantly decreased RBF and IBF. Since biphalin, a non-addictive synthetic opioid, lowers MAP in SHR, a model of hypertension with pronounced neurogenic component, such analogs might find therapeutic application in human stress-induced hypertensive states. Biphalin's advantage is no associated reduction of renal perfusion.

Effects of chymostatin, a chymase inhibitor, on blood pressure, plasma and tissue angiotensin II, renal haemodynamics and renal excretion in two models of hypertension in the rat.

What is the central question of this study? We examined, in hypertensive rats, whether the angiotensin-converting enzyme-independent enzymes generating angiotensin II in the tissues modulate blood pressure, peripheral circulation and renal function. What is the main finding and its importance? The results suggest that chymostatin-sensitive enzymes diminish vascular tone in renal and extrarenal vascular beds. Chymase or similar chymostatin-sensitive enzymes have a significant role in the synthesis of angiotensin II in different tissues but do not control blood pressure in the short term, similarly in salt-dependent or Goldblatt-type rat hypertension. In salt-dependent hypertension, chymase blockade protected renal outer medullary perfusion, probably by reducing the angiotensin II content in the kidney. Chymase is presumed to be a crucial enzyme of the non-angiotensin-converting enzyme pathway of angiotensin II (Ang II) generation in tissues, a process involved in vascular remodelling and development of hypertension. We examined the role of chymase in hypertension induced by exposure of uninephrectomized rats to high dietary salt intake (UNX HS) and in the Goldblatt renal artery stenosis (two-kidney, one-clip) model. In acute experiments with anaesthetized rats of either model, chymostatin at 2 mg kg(-1) h(-1) or 0.05% DMSO solvent was infused i.v. Mean arterial blood pressure, heart rate, iliac blood flow (a measure of hindlimb perfusion), total renal blood flow and intrarenal regional perfusion (laser-Doppler technique) were measured continuously, along with the glomerular filtration rate and renal excretion. In both models, chymase blockade distinctly decreased plasma and tissue Ang II without lowering mean blood pressure or consistently altering the other functional parameters measured. Unexpectedly, in Goldblatt hypertensive rats the blockade increased the renal and hindlimb vascular resistances by 51 and 33%, respectively (P < 0.05). In UNX HS hypertensive rats, chymase blockade abolished the solvent-induced decrease in outer medullary blood flow. We conclude that chymase or similar chymostatin-sensitive enzyme(s) has a significant role in the synthesis of Ang II in different tissues but does not participate in short-term control of blood pressure in salt-dependent or Goldblatt-type rat hypertension. In the Goldblatt model, chymase appeared to reduce the renal and hindlimb vascular resistances by an unknown mechanism. In salt-dependent hypertension, chymase blockade protected renal outer medullary perfusion, probably by reducing Ang II content in the kidney.

The effect of aging on adrenergic and nonadrenergic receptor expression and responsiveness in canine skeletal muscle

We tested the hypothesis that adrenergic and nonadrenergic receptor responsiveness and protein expression would be altered with advancing age. Young (n = 6; 22 ± 1 mo; mean ± SE) and old (n = 6; 118 ± 9 mo) beagles were instrumented with flow probes and an indwelling catheter for continuous measurement of external iliac blood flow and arterial blood pressure. Vascular conductance (VC) was calculated as hindlimb blood flow/mean arterial pressure. Selective agonists for α-1, α-2, neuropeptide-Y (NPY), and purinergic (P2X) receptors were infused at rest and during treadmill running at moderate (2.5 mph) and heavy (4 mph with 2.5% grade) exercise intensities. Feed arteries were dissected from gracilis muscles, and α-1D, α-1B, α-2A, P2X-4, P2X-1, and NPY-Y1 receptor protein expression was determined. Phenylephrine produced similar decreases (P > 0.05) in VC in young and old beagles at rest (young: -62 ± 5%; old: -59 ± 5%) and during moderate (young: -67 ± 5%; old: -62 ± 4%) and heavy (young: -54 ± 4%; old: -49 ± 3%) exercise. Clonidine caused similar (P > 0.05) decreases in VC in old compared with young dogs at rest (young: -59 ± 8%; old: -70 ± 6%) and during moderate (young: -52 ± 6%; old: -47 ± 5%)- and heavy (young: -42 ± 5%; old: -43 ± 5%)-intensity exercise. NPY infusion resulted in a similar decline in VC in young and old beagles at rest (young: -40 ± 7%; old: -39 ± 9%) and during moderate (young: -47 ± 6%; old: -40 ± 6%)- and heavy (young: -40 ± 3%; old: -38 ± 4%)-intensity exercise. α-β-Methylene-ATP also produced similar decreases in VC in young and old beagles at rest (young: -36 ± 6%; old: -40 ± 8%) and during exercise at moderate (young: -42 ± 5%; old: -40 ± 9%) and heavy (young: -47 ± 5%; old: -42 ± 8%) intensities. α-1B receptor protein expression was elevated (P < 0.05) in old compared with young dogs, whereas there were no age-related differences in α-1D or α-2A receptor expression and nonadrenergic P2X-4, P2X-1, and NPY-Y1 receptor expression. The present findings indicate that postsynaptic adrenergic and nonadrenergic receptor responsiveness was not altered by advancing age. Moreover, the expression of adrenergic and nonadrenergic receptors in skeletal-muscle feed arteries was largely unaffected by aging.

Inhibition of Smooth Muscle Myosin as a Novel Therapeutic Target for Hypertension

We examined a novel therapeutic approach for hypertension, a small-molecule direct inhibitor of smooth muscle myosin, CK-2018448 (CK-448), which is an N,N'-alkylurea (U.S. Patent Publication 2009-0275537 A1) in conscious dogs with renal hypertension and compared its efficacy with that of a calcium channel blocker, amlodipine. Dogs were instrumented with a miniature left ventricular pressure gauge, an aortic pressure catheter, and ultrasonic flow probes in the ascending aorta and renal and iliac arteries for measurement of cardiac output and regional blood flow. In the hypertensive state, mean arterial pressure increased from 101 ± 3.8 to 142 ± 1.9 mm Hg. At the doses selected, CK-448 and amlodipine increased cardiac output similarly (30 ± 11% versus 33 ± 6.4%) and similarly reduced mean arterial pressure (-22 ± 3.6% versus -16 ± 3.4%) and total peripheral resistance (-36 ± 5.9% versus -37 ± 5.8%). CK-448 had the greatest vasodilator effect in the renal bed, where renal blood flow increased by 46 ± 9.0%, versus 11 ± 3.4% for amlodipine (p < 0.01). CK-488 produced significantly less vasodilation in the limb, where iliac blood flow did not change; in contrast, it rose by 48 ± 12% with amlodipine (p < 0.01). The minimal effects on limb blood flow could limit the development of peripheral edema, an adverse side effect of Ca(2+) channel blockers. In addition, in a rodent model of hypertension, oral administration of a smooth muscle myosin inhibitor resulted in a sustained antihypertensive effect. Thus, the smooth muscle myosin inhibitor's preferential effect on renal blood flow makes this drug mechanism particularly appealing, because many patients with hypertension have renal insufficiency, and patients with heart failure could benefit from afterload reduction coupled with enhanced renal blood flow.

Magnetically targeted thrombolysis with recombinant tissue plasminogen activator bound to polyacrylic acid-coated nanoparticles

We investigated the feasibility and efficacy of target thrombolysis with recombinant tissue plasminogen activator (rtPA) covalently bound to magnetic nanoparticle (MNP) and retained to the target site in vivo by an external magnet. Polyacrylic acid-coated magnetite (PAA–MNP, 246 nm) was synthesized and characterized; rtPA was immobilized to PAA–MNP through carbodiimide-mediated amide bond formation. The enzyme activities of the bound rtPA, as measured by a chromogenic substrate assay and 125I-fibrinolysis assay, were 87 ± 1% and 86 ± 3% of that of free rtPA. Under guidance with the magnet moving back and forth along the iliac artery, the thrombolytic activity of PAA–MNP–rtPA with rtPA equivalent to 0.2 mg/kg was determined by flowmetry in a rat embolic model. Intra-arterial administration of PAA–MNP–rtPA restored the iliac blood flow within 75 min to 82% of that before the clot lodging, whereas equivalent amount of PAA–MNP or free rtPA exerted no improvement on hemodynamics. At the end of 2-h period, PAA–MNP–rtPA did not alter levels of hemoglobin, hematocrit, or blood cell count. In conclusion, immobilization of rtPA to PAA–MNP with covalent binding resulted in a stable rtPA preparation and predictable amount of rtPA around the target site under magnetic guidance; this approach may achieve reproducible and effective target thrombolysis with <20% of a regular dose of rtPA.

Alpha-adrenoceptor-mediated vasoconstriction is not involved in impaired functional vasodilation in the obese Zucker rat.

1. Obesity/metabolic syndrome is associated with augmented a-adrenoceptor sensitivity and impaired hyperaemic responses to exercise. Thus, it is possible that this elevated a-adrenoceptor constriction contributes to the blunted hyperaemic response. 2. Male lean and obese Zucker rats were instrumented for acute measurements of blood pressure (BP) and iliac blood flow (BF). Changes in BP and BF were determined in anaesthetized animals in response to intravenous administration of increasing doses of the a(1)-adrenoceptor agonist phenylephrine (PE). Once BF and BP returned to normal, a single bolus of the a-adrenoceptor antagonist phentolamine (0.5 mg) was administered. In separate animals, the spinotrapezius muscle was exteriorized for direct in situ observation of the microcirculation in response to phentolamine and muscle contraction. 3. Administration of PE demonstrated that iliac BF is highly autoregulated in the face of increasing perfusion pressure. Iliac conductance following phentolamine was significantly greater in obese rats. Following phentolamine administration, iliac vascular conductance was significantly greater in obese rats compared with lean animals. However, a-adrenoceptor blockade did not significantly alter arteriolar diameter in the spinotrapezius muscle during muscle contraction in either lean or obese animals. 4. These results suggest a greater contribution of the a-adrenoceptors in basal hindlimb vascular tone in obese rats. Furthermore, an augmented a-adrenoceptor-mediated vasoconstriction may not contribute to the impaired functional dilation in anaesthetized obese rats.

THE POTENTIAL ROLE OF THE ADRENAL MEDULLA IN HEMODYNAMIC RESPONSES DURING GABA ACTIVATION OF RAT AREA POSTREMA

The goal of this study was to investigate the potential role of the adrenal medulla in the multiple cardiovascular alterations that occur during activation of GABA(A) subtype in the area postrema. Blood pressure, heart rate, renal, iliac blood flows and plasma catecholamines were monitored during nonaliter infusion of muscimol (10 nl/min/10min, 1ng/nl) in the area postrema of the rats. Responses in pentobarbital-anesthetized male Albino rats, either intact (CON) or acutely adrenalectomized (ADX), were compared. Muscimol infusion increased mean arterial pressure in a dose-dependent manner in CON, but in ADX group such pressor effect was significantly attenuated. Heart rate was not significantly affected by drug infusion in either group. Renal bed actively constricted with non-significant transient increase in renal blood flow in both groups. Iliac blood flow increased markedly in CON, but remained unchanged in ADX. Iliac resistance was increased significantly in both CON and ADX, but it was rapidly attenuated to control values in CON. Plasma catecholamine concentrations was significantly elevated by muscimol infusion. We conclude that activation GABA(A) subtype may augment sympathetic outflow to the adrenals causing catecholamine release that in turn produces iliac bed vasodilation, but renal bed vasoconstriction. In ADX, this dominant effect of adrenal sympathetic activation was acutely attenuated because of withdrawal of sympathetic vasomotor tone in these resistance beds.

Prolactin Induces Regional Vasoconstriction through the β2-Adrenergic and Nitric Oxide Mechanisms

Prolactin has been associated with many effects and has been implicated in the pathogenesis of pregnancy-related hypertensive disorders, although little is known about its vascular effects. The present study was designed to determine the primary effect of prolactin on regional vascular beds and the mechanisms involved. In 37 anesthetized pigs, the infusion of 0.17 mug/kg min of prolactin at constant heart rate and arterial pressure decreased coronary, mesenteric, renal, and iliac blood flow. This response was graded in further five pigs by increasing the infused dose of the hormone between 0.017 and 1 mug/kg min. In 22 of the 37 pigs, blockade of cholinergic receptors (five pigs) and of alpha-adrenoceptors (five pigs) did not affect the prolactin-induced vascular response, which was abolished by blockade of beta(2)-adrenoceptors (five pigs) and by blockade of vascular nitric oxide (NO) synthase (seven pigs). In 15 of the 37 pigs the increases in measured blood flows caused by iv infusion of isoproterenol (five pigs) and by intraarterial administration of acetylcholine (five pigs) and of sodium nitroprusside (five pigs) were significantly reduced by infusion of prolactin. Moreover, the treatment of porcine aortic endothelial cells by prolactin caused a reduction of NO production and of the phosphorylation of ERK, Akt, and p38, which was prevented by the concomitant treatment by the beta(2)-adrenergic agonist albuterol. The present study showed that iv infusion of prolactin primarily caused coronary, mesenteric, renal, and iliac vasoconstriction. These effects were brought about by the inhibition of a vasodilatory beta(2)-adrenergic receptor-mediated effect related to the NO intracellular pathway.

The 5-Hydroxytryptamine1A Receptor Agonist, (+)-8-Hydroxy-2-(di-n-propylamino)-tetralin, Increases Cardiac Output and Renal Perfusion in Rats Subjected to Hypovolemic Shock

The 5-hydroxytryptamine(1A) receptor agonist, (+)-8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), raises blood pressure (BP) and venous tone in rats subjected to hemorrhagic shock. Here, BP, ascending aortic blood flow [i.e., estimate of cardiac output (CO)] and venous blood gases were measured to determine the hemodynamic effects of 8-OH-DPAT (30 nmol/kg i.v., n = 10), saline (n = 10), or an equipressor infusion of epinephrine (n = 10) in unanesthetized rats subjected to hemorrhagic shock (25 min of hypotensive hemorrhage, approximately 50 mm Hg). Renal and iliac blood flow were measured in separate groups of similarly hemorrhaged rats given the same dose of 8-OH-DPAT (n = 7) or saline (n = 6). Compared with saline treatment, 8-OH-DPAT produced a sustained rise in BP (+32 +/- 4 versus +9 +/- 2 mm Hg, 15 min after injection, P < 0.01) and CO (+27 +/- 5 versus +4 +/- 6 ml/min/kg, P < 0.01) but did not affect total peripheral resistance (TPR). Infusion of epinephrine reduced CO (-12 +/- 6 ml/min/kg, P < 0.01) and dramatically increased TPR [+0.37 +/- 0.11 versus +0.05 +/- 0.05 log (mm Hg/ml/min/kg), P < 0.01]. 8-OH-DPAT increased renal conductance (+7 +/- 1 versus +4 +/- 1 microl/min/mm Hg, P < 0.01) but did not significantly affect iliac conductance. 8-OH-DPAT attenuated further development of acidosis compared with either saline or epinephrine (-5.6 +/- 1.6 versus -13.0 +/- 2.0 versus -11.3 +/- 2.6 mmol/liter base excess 45 min after start of hemorrhage, both P < 0.01 versus 8-OH-DPAT). These data demonstrate that 8-OH-DPAT improves hemodynamics during circulatory shock, in part, through renal vasodilation and mobilizing of blood stores.