Dog Heart Research Articles

98. Long-Term Robust Myocardial Transduction of the Dog Heart from Peripheral Vein by Adeno-Associated Virus Serotype-8 (AAV-8)

98. Long-Term Robust Myocardial Transduction of the Dog Heart from Peripheral Vein by Adeno-Associated Virus Serotype-8 (AAV-8)

Defects in Free Fatty Acid Oxidation and Glucose Oxidation Coexist in the Failing Heart

Purpose Abnormalities of energy substrate utilization exist in the failing heart and contribute to disease progression. These abnormalities are attributed by some to decreased glucose utilization and by others to reduced free fatty acid (FFA) oxidation. In the normal heart, recruitment of the glucose transport proteins GLUT-1 and -4 is a mechanism by which the heart increases glucose transport for metabolism while up- or down-expression of muscle carnitine palmitoyl transferase (mCPT-1) provides directionally concordant regulation of FFA oxidation. In the present study we tested the hypothesis that defects of both GLUT-1 and -4 and mCPT-1 coexist in the failing LV myocardium. Methods and Materials Studies were performed in LV tissue homogenate obtained from 6 normal (NL) donor human hearts, 6 explanted failing human hearts with dilated cardiomyopathy (DCM) and 6 failing human hearts with ischemic cardiomyopathy (ICM) and from 6 NL and 7 coronary microembolization-induced heart failure (HF) dogs. Protein levels of the glucose transporters, GLUT-1 and -4 where measured in human and dog hearts and mCPT-1 in dog hearts using specific antibodies and Western blotting and bands quantified in densitometric units (du). Results Compared to NL, protein levels of GLUT-1 and -4 were significantly decreased in DCM, ICM and HF dogs and mCPT-1 was significantly decreased in HF dogs (Table). Conclusions Abnormalities of key regulators of FFA oxidation and glucose oxidation coexist in the failing heart regardless of HF etiology and favor energy deprivation. Coexistence of these abnormalities in the failing heart can act to limit the benefits that may be derived from therapies that target. Protein Expression in LV MyocardiumNL-Human DonorDCMICMGLUT-1 (du)15.7 ± 0.910.6 ± 0.3 * 0.41 ± 0.02 * GLUT-4 (du)31.7 ± 1.719.5 ± 1.8 * 16.6 ± 1.4 * NL-DogHF-DogGLUT-1 (du)20.1 ± 3.04.7 ± 0.5 † GLUT-4 (du)24.5 ± 3.116.2 ± 0.8 † mCPT-1 (du)1.40 ± 0.070.53 ± 0.06 † *=p

LONG-TERM THERAPY WITH BENDAVIA (MTP-131), A NOVEL MITOCHONDRIA-TARGETING PEPTIDE, REVERSES MITOCHONDRIAL FUNCTIONAL ABNORMALITIES IN LEFT VENTRICULAR MYOCARDIUM OF DOGS WITH ADVANCED HEART FAILURE

Mitochondria (MITO) of failed human hearts and hearts of dogs with experimental heart failure (HF) manifest abnormalities characterized by reduced state-3 respiration, reduced membrane potential (Δψm) and increased opening of membrane permeability transition pores (mPTP). These abnormalities lead

Altered calsequestrin glycan processing is common to diverse models of canine heart failure

Calsequestrin-2 (CSQ2) is a resident glycoprotein of junctional sarcoplasmic reticulum that functions in the regulation of SR Ca(2+) release. CSQ2 is biosynthesized in rough ER around cardiomyocyte nuclei and then traffics transversely across SR subcompartments. During biosynthesis, CSQ2 undergoes N-linked glycosylation and phosphorylation by protein kinase CK2. In mammalian heart, CSQ2 molecules subsequently undergo extensive mannose trimming by ER mannosidase(s), a posttranslational process that often regulates protein breakdown. We analyzed the intact purified CSQ2 from mongrel canine heart tissue by electrospray mass spectrometry. The average molecular mass of CSQ2 in normal mongrel dogs was 46,306 ± 41 Da, corresponding to glycan trimming of 3-5 mannoses, depending upon the phosphate content. We tested whether CSQ2 glycan structures would be altered in heart tissue from mongrel dogs induced into heart failure (HF) by two very different experimental treatments, rapid ventricular pacing or repeated coronary microembolizations. Similarly dramatic changes in mannose trimming were found in both types of induced HF, despite the different cardiomyopathies producing the failure. Unique to all samples analyzed from HF dog hearts, 20-40 % of all CSQ2 contained glycans that had minimal mannose trimming (Man9,8). Analyses of tissue samples showed decreases in CSQ2 protein levels per unit levels of mRNA for tachypaced heart tissue, also indicative of altered turnover. Quantitative immunofluorescence microscopy of frozen tissue sections suggested that no changes in CSQ2 levels occurred across the width of the cell. We conclude that altered processing of CSQ2 may be an adaptive response to the myocardium under stresses that are capable of inducing heart failure.

The Dynamic Function of the Atrial Diastole of the Heart and Motion of Venous Valves in Humans

This study demonstrates dynamic function of atrial diastole for the first time in the history of medicine, following the revelation of ventricular function by Sir William Harvey. This study consists of two parts. First part is the study of humans and the discovery of the rhythmic opening and closing of venous valves in the femoral vein segment during each cardiac cycle under fluoroscopy. Its relationship to the right atrial diastole is discussed. Second part is an experimental model developed in a dog's heart. Experiments are conducted in an erect posture, in which the right atrium is partially and totally isolated physically and/or functionally. The right atrium was found to function as a suction pump, readily demonstrated on graphic curves by voluntary stretching of muscle fibers of the empty atrium, creating considerable negative pressure during diastolic function, and responsible for venous return to the heart. Motive forces in the venous return are common knowledge in present medical literature, but are limited to respiration and skeletal muscle contraction of the extremities. The discovery of the right atrium as a suction force due to stretching of muscle fibers during diastolic function, thereby creating negative pressure, represents a departure from the currently accepted paradigm established by Sir William Harvey (1576-1652), with the heart as an organ functioning solely by contraction of its chambers. This is the first time since then a fundamental new discovery concerning cardiac mechanical function has been made utilizing experimental evidence.

Interventricular comparison of the energetics of contraction of trabeculae carneae isolated from the rat heart

We compare the energetics of right ventricular and left ventricular trabeculae carneae isolated from rat hearts. Using our work-loop calorimeter, we subjected trabeculae to stress-length work (W), designed to mimic the pressure-volume work of the heart. Simultaneous measurement of heat production (Q) allowed calculation of the accompanying change of enthalpy (H = W + Q). From the mechanical measurements (i.e. stress and change of length), we calculated work, shortening velocity and power. In combination with heat measurements, we calculated activation heat (Q(A)), crossbridge heat (Q(xb)) and two measures of cardiac efficiency: 'mechanical efficiency' ((mech) = W/H) and 'crossbridge efficiency' ((xb) = W/(H - Q(A))). With respect to their left ventricular counterparts, right venticular trabeculae have higher peak shortening velocity, and higher peak mechanical efficiency, but with no difference of stress development, twitch duration, work performance, shortening power or crossbridge efficiency. That is, the 35% greater maximum mechanical efficiency of right venticular than left ventricular trabeculae (13.6 vs. 10.2%) is offset by the greater metabolic cost of activation (Q(A)) in the latter. When corrected for this difference, crossbridge efficiency does not differ between the ventricles.

Comparative Analysis of the Effects of Omeprazole and Ischemic Preconditioning in Protection against Ischemia and Reperfusion Myocardial: Experimental Study in Isolated Rat Hearts

Introduction: Myocardial protection against ischemic injury has been a major focus of studies of cardiovascular sciences worldwide. In 1986, Murry et al. became pioneers by showing a special ischemic preconditioning technique in hearts of dogs which motivated researches for better understanding of endogenous protective mechanisms of the human heart. The aim of this study was to evaluate the effects of omeprazole on protection of functional recovery of isolated rat hearts subjected to ischemia-reperfusion with and without ischemic preconditioning (IP). Methods: In five groups of eight Wistar breed rats, the hearts were removed after anesthesia and perfused with Krebs-Henseleit solution (95% O2, 5% CO2, 37oC). The GI was a control group. The GII, GIII, GIV and GV, hearts were submitted to ischemia (20 min) and reperfusion (30 min). In GIV and GV, preconditioning was performed with 5 min of ischemia and 5 min of reperfusion before 20 min of the ischemia period induction. In GIII and GV Omeprazole 200 μg was done before a 20 min-period of ischemia induction. Heart Rate (HR), Coronary Flow (CF), Systolic Pressure (SP), +dP/dt and−dP/dt were registered before (t0) and after reperfusion (t30). Kruskal-Wallisand Mann - Whitney (p<0.05) test were used. Results: The CF analysis showed that the Groups II, III, IV and V, had a similar behavior analyzed over time (p=0.316). Group I presented the averages 18.6, 17.5 and 16.6 at t0, t15’ and t30’ respectively, with significant changes in the pattern of behavior analyzed over time (p<0.001). There were no significant differences in the HR, SP, +dP/dtmax, and −dP/dtmax between Groups I, III, IV and V results. Conclusion: Omeprazole conferred preconditioning characteristics to isolated rat hearts subjected to ischemic injury. There was no greater efficacy of protection shown in relation to existing methods of ischemic preconditioning. There was no synergism in the use of omeprazole in conjunction with the methods of IP.

Роль оценочного компонента значения лексемы глаза в произведениях М.А. Булгакова «Собачье сердце» и «Роковые яйца»

Роль оценочного компонента значения лексемы глаза в произведениях М.А. Булгакова «Собачье сердце» и «Роковые яйца»

Análise comparativa entre a vascularização arterial ventricular e do nó sinoatrial em corações de cães

Utilizamos nesta pesquisa 40 corações de cães adultos, machos e fêmeas, de idades variadas, que não portavam nenhuma afecção cardíaca. Os corações tiveram as artérias coronárias injetadas, separadamente, com Neoprene Látex 450, corado com pigmento vermelho, e posteriormente dissecados. Em todas estas preparações verificamos que na vascularização dos ventrículos predominava a artéria coronária esquerda que fornecia os ramos interventriculares paraconal e subsinuoso. Já, a região ocupada pelo nó sinoatrial ficava mais frequentemente (17 vezes, 42,5%) na dependência do ramo proximal atrial esquerdo ou de colateral deste vaso, oriundo do ramo circunflexo esquerdo, ou deste vaso associado ao ramo distal atrial direito (8 vezes, 20%), procedente do ramo circunflexo direito. Com menor frequência (14 vezes, 30%), a área tomada pelo nó sinoatrial, encontramos apenas colaterais do ramo circunflexo direito, mais exatamente somente o ramo distal atrial direito (10 vezes, 25%), apenas o ramo proximal atrial direito (3 vezes, 7,5%) ou ainda exclusivamente o ramo intermédio atrial direito (1 vez, 2,5%). Em um único caso (1 vez, 2,5%) no território do nó sinoatrial observamos apenas colateral do ramo circunflexo esquerdo, isto é o ramo distal atrial esquerdo. A análise destes resultados permite concluir, que nesta espécie não existe qualquer tipo de relação entre o tipo de vascularização dos ventrículos e a irrigação do nó sinoatrial. Sendo assim, considerar os ramos ventriculares isoladamente não é suficiente para um entendimento clínico-cirúrgico aplicado, uma vez que os ramos atriais apresentam uma importante contribuição para a vascularização do nó sinoatrial.

The Effect of the Cinnamon on Dog's Heart Performance by Focus on Korotkoff Sounds

The Effect of the Cinnamon on Dog's Heart Performance by Focus on Korotkoff Sounds

MK-0448, a Specific Kv1.5 Inhibitor

Background— We evaluated the viability of I Kur as a target for maintenance of sinus rhythm in patients with a history of atrial fibrillation through the testing of MK-0448, a novel I Kur inhibitor. Methods and Results— In vitro MK-0448 studies demonstrated strong inhibition of I Kur with minimal off-target activity. In vivo MK-0448 studies in normal anesthetized dogs demonstrated significant prolongation of the atrial refractory period compared with vehicle controls without affecting the ventricular refractory period. In studies of a conscious dog heart failure model, sustained atrial fibrillation was terminated with bolus intravenous MK-0448 doses of 0.03 and 0.1 mg/kg. These data led to a 2-part first-in-human study: Part I evaluated safety and pharmacokinetics, and part II was an invasive electrophysiological study in healthy subjects. MK-0448 was well-tolerated with mild adverse experiences, most commonly irritation at the injection site. During the electrophysiological study, ascending doses of MK-0448 were administered, but no increases in atrial or ventricular refractoriness were detected, despite achieving plasma concentrations in excess of 2 μmol/L. Follow-up studies in normal anesthetized dogs designed to assess the influence of autonomic tone demonstrated that prolongation of atrial refractoriness with MK-0448 was markedly attenuated in the presence of vagal nerve simulation, suggesting that the effects of I Kur blockade on atrial repolarization may be negated by enhanced parasympathetic neural tone. Conclusions— The contribution of I Kur to human atrial electrophysiology is less prominent than in preclinical models and therefore is likely to be of limited therapeutic value for the prevention of atrial fibrillation.

Abstract 9642: Prolongation of AERP and APD with the Selective IKur inhibitor, BMS-394136, is Increased in the Zucker Diabetic Fatty Rat

Introduction: Diabeties mellitus is a risk factor for atrial fibrillation (AF). We previously reported that atrial ischemia increases activity of a selective IKur inhibitor, BMS-394136, on atrial effective refractory period (AERP) and action potential duration (APD) without effecting ventricular effective refractory period (VERP) in dog heart. This study evaluated the efficacy of BMS-394136 on AERP and APD in Zucker Diabetic Fatty (ZDF) rats. Methods: Male ZDF370 (obese and diabetic) and ZDF371 (lean control) rats on normal diet, averaging 7 months of age, were entered into the study. After induction of anesthesia, a 2F multielectrode was placed into right ventricle to measure VERP. BMS-394136 (10 mg/kg) was infused over 5 min through the jugular vein. After VERP assessment, hearts were removed and perfused in a Langendorff apparatus with Tyrode’s buffer for assessment of AERP and APD at BMS-394136 concentrations of 1.0, 3.0 and 10.0 µM, respectively. After Langendorff perfusion, atrial strips were removed and studied with standard microelectrode techniques in perfusion. Results: (*p&lt;0.05). The average weight and blood glucose was 367g and &gt;600mg/dl in the ZDF370 rats and 465g* and 253* mg/dl in the ZDF371 rats. VERP was prolonged by BMS-394136 in vivo by 21±1.7 ms (39%) in ZDF370 rats (n=10), and by 24±1.7 ms (50%) in ZDF371 rats. No differences in APD100 (64±4ms vs 64±3 ms) or AERP (29±2ms vs 25±2ms) were observed at baseline in Langendorff mode from ZDF370 and ZDF371 hearts (n=4/each). However, BMS-394136 dose-dependently prolonged APD100 and AERP to a greater extent in ZDF370 rats at 1.0µM (11%* and 36%*), 3.0µM (27%* and 44%*) and 10.0µM (33%* and 64%*) than in ZDF371 rats at 1.0µM (-2%* and 3%), 3.0µM (3% and 3%) and 10.0 µM (8% and 14%). In atrial strips (n=4), BMS-394136 increased APD30 by (%) 0±2, 22±3, 33±2*, APD50 by(%) 14±4, 36±5, 32±7, 50±4* and APD90 by (%)3±4, 14±9, 23±5* at concentrations of 1.0µM, 3.0µM and 10.0 μ M in ZDF370 rats, no effect was observed on APD prolongation in ZDF371 rats. Conclusions: Diabeties mellitus may increase the efficacy of the selective IKur inhibitor, BMS-394136, on prolongation of AERP and APD. The absence of effect with BMS-394136 on VERP confirms the atrial selective activity of this compound or ion channel remodeling.

Ranolazine Causes Atrial-Selective Electrophysiological Effects and Suppresses the Induction of Atrial Fibrillation in a Canine Model of Heart Failure

Background Heart failure (HF) and atrial fibrillation (AF) frequently coexist. There is a critical need for safer and more effective pharmacologic treatment of AF in the setting of HF. The atrial-selective electrophysiologic (EP) effects as well as anti-AF efficacy of ranolazine (RAN) have been demonstrated in healthy canine atria. In the current study, we investigated the EP and anti-AF effects of a clinically relevant concentration of RAN (5 μM) in coronary-perfused right atrial (RA) and left ventricular (LV) preparations isolated from the hearts of HF dogs. Methods HF was induced by ventricular tachypacing (2–6 weeks at 200–240 bpm; n=17 dogs). Transmembrane action potentials were recorded using standard microelectrode techniques. Results A single premature beat reproducibly induced AF in 10/17 atria lasting up to 20 minutes. RAN (5 μM) suppressed induction of AF in 7/10 atria. In the remaining 3 atria, ranolazine slowed AF frequency and reduced the duration. In RA, RAN caused little change in action potential duration (APD 70 : from 105 ± 12 to 114 ± 15 ms, P = NS) but significantly prolonged effective refractory period ([ERP] from 127 ± 21 to 176 ± 25 ms, P max ) decreased (229 ± 55 vs 189 ± 50 V/s), diastolic threshold of excitation (DTE) increased (0.24 ± 0.05 vs 0.42 ± 0.16 mA), and P-wave duration (atrial conduction time) prolonged in response to 5 μM RAN (31.6 ± 7.6 vs 36.5 ± 6.5 ms, P 90 , ERP, DTE, V max , and QRS duration (n = 5–6). Conclusions Our results demonstrate the effect of a relatively low concentration of RAN to suppress induction of AF much more effectively (70%) in an HF model of AF than previously described in vagal models of AF. In both models, depression of peak sodium channel current-dependent parameters is atrial selective. In view of the clinical safety of RAN (MERLIN-TIMI 36), our results suggest a need for studies specifically designed to evaluate the clinical utility of RAN for rhythm control of AF in patients with HF.

Effects of ganglionated plexi ablation on ventricular electrophysiological properties in normal hearts and after acute myocardial ischemia

BackgroundGanglionated plexi (GP) ablation has been shown to play an important role in atrial fibrillation (AF) initiation and maintenance. Also, GP ablation increases chances for prevention of AF recurrence. This study investigated the effects of GP ablation on ventricular electrophysiological properties in normal dog hearts and after acute myocardial ischemia (AMI). MethodsFifty anesthetized dogs were assigned into normal heart group (n=16) and AMI heart group (n=34). Ventricular dynamic restitution, effective refractory period (ERP), electrical alternans and ventricular fibrillation threshold (VFT) were measured before and after GP ablation in the normal heart group. In the AMI heart group, the incidence of ventricular arrhythmias and VFT were determined. ResultsIn the normal heart group, GP ablation significantly prolonged ERP, facilitated electrical alternans but did not increase ERP dispersion, the slope of restitution curves and its spatial dispersion. Also, GP ablation did not cause significant change of VFT. In the AMI heart group, the incidence of ventricular arrhythmias after GP ablation was significantly higher than that in the control group or the GP plus stellate ganglion (SG) ablation group (P<0.05). Spontaneous VF occurred in 8/12, 1/10 and 2/12 dogs in the GP ablation group, the GP plus SG ablation group and the control group, respectively (P<0.05). VFT in the GP ablation group showed a decreased trend though a significant difference was not achieved compared with the control or the GP plus SG ablation group. ConclusionsGP ablation increases the risk of ventricular arrhythmias in the AMI heart compared to the normal heart.

Comparison of the Gibbs and Suga formulations of cardiac energetics: the demise of “isoefficiency”

Two very different sorts of experiments have characterized the field of cardiac energetics over the past three decades. In one of these, Gibbs and colleagues measured the heat production of isolated papillary muscles undergoing isometric contractions and afterloaded isotonic contractions. The former generated roughly linear heat vs. force relationships. The latter generated enthalpy-load relationships, the peak values of which occurred at or near peak isometric force, i.e., at a relative load of unity. Contractile efficiency showed a pronounced dependence on afterload. By contrast, Suga and coworkers measured the oxygen consumption (Vo(2)) while recording the pressure-volume-time work loops of blood-perfused isolated dog hearts. From the associated (linear) end-systolic pressure-volume relations they derived a quantity labeled pressure-volume area (PVA), consisting of the sum of pressure-volume work and unspent elastic energy and showed that this was linearly correlated with Vo(2) over a wide range of conditions. This linear dependence imposed isoefficiency: constant contractile efficiency independent of afterload. Neither these data nor those of Gibbs and colleagues are in dispute. Nevertheless, despite numerous attempts over the years, no demonstration of either compatibility or incompatibility of these disparate characterizations of cardiac energetics has been forthcoming. We demonstrate that compatibility between the two formulations is thwarted by the concept of isoefficiency, the thermodynamic basis of which we show to be untenable.

Abstract 26: Myocardial Phosphodiesterase-2A Is Upregulated in Human and Experimental Heart Failure and Blunts Cardiac β-Adrenergic Inotropic Responsiveness

Augmented cGMP- and diminished cAMP-signaling within cardiomyocytes is characteristic for failing hearts. Cyclic nucleotide phosphodiesterases (PDEs) comprise a family of cyclic-nucleotide hydrolyzing enzymes, controlling cAMP and cGMP levels. Among them the PDE-2A isoform has the unique property to be stimulated by cGMP but primarily hydrolyzing cAMP. This appears to mediate a negative cross-talk between both signaling pathways. However, a potential role for PDE-2A in the failing heart has not been addressed yet. Here we show that PDE-2A protein levels were ∼2-fold higher in failing human hearts as well as in a large animal heart failure model from dog hearts subjected to rapid-pacing (n≥6, p&lt;0.05). Intriguingly, PDE-2A protein levels were normal in hypertrophied hearts from patients with preserved cardiac function who underwent aortic valve replacement. Chronic beta-adrenergic stimulation by catecholamine infusions enhanced cAMP hydrolyzing activity of PDE-2A by four-fold (n≥6, p&lt;0.05) in rat hearts in vivo and in isolated cardiomyocytes (measured by radioimmunoassay and FRET-based sensors, respectively) and correlated with blunted beta-adrenergic responsiveness. Consistent with this observation, overexpressed PDE-2A, which localized to the sarcomeric Z-line, blunted the rise in cAMP by 70% (n≥6, p&lt;0.05) and abolished the positive inotropic effect after acute beta-adrenergic stimulation by 70% (n≥6, p&lt;0.05) in isolated cardiomyocytes. Notably, those cardiomyocytes also showed marked protection from norepinephrine-induced hypertrophic responses, e. g. 40% less increase in cell surface area (n≥10, p&lt;0.05). In summary, PDE-2A is markedly upregulated in human and experimental failing hearts. This may constitute an important defense mechanism during cardiac stress, by antagonizing the cAMP-mediated toxic effects. Thus, activating myocardial PDE-2A may represent a new intracellular anti-adrenergic therapeutic strategy in heart failure.

Fragment of a receipt

Fragment of a receipt Breyten Breytenbach (bio) I saw a pumpkin-faced man soaking his dry red beard in a beaker of winter-night black beer refusing to pay and disgusted I left the tavern and outside I saw a youth with one rotten little hand held uselessly like a limp rose to his chest he wore pink shoes and I walked down the splash-wet road with wind in my trouser legs past a tree leaning into the road with its branches rested on a ring wall whistling at the girls and I entered a blue door up the stairs and showed my teeth in a narrow smile to a cat and a dog and a snot-nosed baby and a woman with cruddy toenails and a man with shoulders as apologetic as the knees of schoolgirls and I sat down on a chair and ate fish and ketchup and radishes and peas and potatoes in their jackets and butter and bread and salad and sweets and burped and laughed and I heard the rain like the sharp claws of pigeons on the roof against the windows and an aircraft god knows how high in the sky and I looked into the green bumps of the man's eyes and looked away and looked again and trod on the cat's tail and got up and scratched my ear and surreptitiously let go a fart in the corner and walked down the stairs out the blue door and saw that the road was wild and blue like a winter sky and walked in it and with commiseration thought about the fate of my poor soaked toes but never mind and I saw a man holding up a lamppost and a woman peeling potatoes on the sidewalk and mountains looming above the towers of the cathedrals of a town and a bus tinkling like an old piano and a newspaper with a hat on the steps of an apartment block and a sparrow with bare feet perched and smoking in a palm tree and I told all my sweet secrets to my nose and ears. [End Page 162] Breyten Breytenbach Breyten Breytenbach is a poet, novelist, memoirist, essayist, and visual artist, and a well-known human rights activist. His paintings and drawings have been exhibited around the world. Born in South Africa, he immigrated to Paris in the late 1960s and became deeply involved in the anti-Apartheid movement. Breytenbach's works include A Season in Paradise (1980), Mouroir (1983), Notes from the Middle World (2009), All One Horse (1989), The Memory of Birds in Times of Revolution (1996), Dog Heart (1998), and Voice Over: A Nomadic Conversation with Mahmoud Darwish (Archipelago Books, 2009). His many honors include the Alan Paton Award for Return to Paradise in 1994 and the prestigious Hertzog Prize for Poetry for Papierblom in 1999 and Die Windvanger in 2008. Copyright © 2012 Middlebury College Publications

Sulfonylurea Receptor Subunit Composition of KATP Channels in Dog and Human Hearts

ATP sensitive potassium (KATP) channels are assembled by four pore-forming inward rectifier subunits (Kir6.1 or Kir6.2), each associated with one sulfonylurea subunit (SUR1 or SUR2). The differential subunit composition defines distinct KATP channel properties and tissue-specific function. Although the consensus has been that cardiac KATP channels are SUR2A-based channels, our recent studies indicate that mouse cardiac KATP channels are chamber-specific: SUR1-based channels in atria vs. SUR2A-based channels in ventricles. To test whether chamber specificity is an universal property of cardiac KATP channels in other species, whole-cell and inside-out excised patch-clamp techniques were applied to examine the effects of SUR- specific channel openers (pinacidil acts on SUR2A and diazoxide on SUR1) on isolated dog and human cardiomyocytes. In dog atria, pinacidil- and diazoxide-induced whole-cell currents were 40 ± 4 pA/pF (n = 14) and 13 ± 6 pA/pF (n = 11, p 0.05), respectively; while the ventricular currents were 117 ± 75 pA (n = 3) and 92 (n = 1), respectively. The results indicate that SUR2A-based channels are predominant in dog heart, while abundant SUR1- and SUR2A-based channels co-exist in human heart, in both atria and ventricles. Therefore, there is marked variability between all three species studied, which should be considered carefully when using either mice or dogs to model the effects of human channels in either normal or diseased human hearts.

Experimental Mapping of the Canine KCNJ2 and KCNJ12 Gene Structures and Functional Analysis of the Canine KIR2.2 ion Channel

For many model organisms traditionally in use for cardiac electrophysiological studies, characterization of ion channel genes is lacking. We focused here on two genes encoding the inward rectifier current, KCNJ2 and KCNJ12, in the dog heart. A combination of RT-PCR, 5′-RACE, and 3′-RACE demonstrated the status of KCNJ2 as a two exon gene. The complete open reading frame (ORF) was located on the second exon. One transcription initiation site was mapped. Four differential transcription termination sites were found downstream of two consensus polyadenylation signals. The canine KCNJ12 gene was found to consist of three exons, with its ORF located on the third exon. One transcription initiation and one termination site were found. No alternative splicing was observed in right ventricle or brain cortex. The gene structure of canine KCNJ2 and KCNJ12 was conserved amongst other vertebrates, while current GenBank gene annotation was determined as incomplete. In silico translation of KCN12 revealed a non-conserved glycine rich stretch located near the carboxy-terminus of the KIR2.2 protein. However, no differences were observed when comparing dog with human KIR2.2 protein upon ectopic expression in COS-7 or HEK293 cells with respect to subcellular localization or electrophysiological properties.

Cardiovascular System Modeling

Cardiovascular System Modeling