Pauline Jamieson

Understanding the role of glucocorticoids in obesity: tissue-specific alterations of corticosterone metabolism in obese Zucker rats

The role of glucocorticoids in obesity is poorly understood. Observations in obese men suggest enhanced inactivation of cortisol by 5alpha-reductase and altered reactivation of cortisone to cortisol by 11betahydroxysteroid dehydrogenase type 1 (11betaHSD1). These changes in glucocorticoid metabolism may influence corticosteroid receptor activation and feedback regulation of the hypothalamic-pituitary-adrenal axis (HPA). We have compared corticosterone metabolism in vivo and in vitro in male obese and lean Zucker rats, aged 9 weeks (n = 8/group). Steroids were measured in 72-h urine and 0900 h trunk blood samples. 5alpha-Reductase type 1 and 11betaHSD activities were assessed in dissected tissues. Obese animals were hypercorticosteronemic and excreted more total corticosterone metabolites (2264+/-623 vs. 388+/-144 ng/72 h; P = 0.003), with a greater proportion being 5alpha-reduced or 11-oxidized. 11-Dehydrocorticosterone was also elevated in plasma (73+/-9 vs. 18+/-2 nM; P = 0.001) and urine (408+/-111 vs. <28 ng/72 h; P = 0.01). In liver of obese rats, 5alpha-reductase type 1 activity was greater (20.6+/-2.7% vs. 14.1+/-1.5%; P<0.04), but 11betaHSD1 activity (maximum velocity, 3.43+/-0.56 vs. 6.57+/-1.13 nmol/min/mg protein; P = 0.01) and messenger RNA levels (0.56+/-0.08 vs. 1.03+/-0.15; P = 0.02) were lower. In contrast, in obese rats, 11betaHSD1 activity was not different in skeletal muscle and sc fat and was higher in omental fat(36.4+/-6.2 vs. 19.2+/-6.6; P = 0.01), whereas 11betaHSD2 activity was higher in kidney (16.7+/-0.6% vs. 11.3+/-1.5%; p = 0.01). We conclude that greater inactivation of glucocorticoids by 5alpha-reductase in liver and 11betaHSD2 in kidney combined with impaired reactivation of glucocorticoids by 11betaHSD1 in liver may increase the MCR of glucocorticoids and decrease local glucocorticoid concentrations at these sites. By contrast, enhanced 11betaHSD1 in omental adipose tissue may increase local glucocorticoid receptor activation and promote obesity.

Tissue- and temporal-specific regulation of 11β-hydroxysteroid dehydrogenase type 1 by glucocorticoids in vivo

11Beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1) catalyses the interconversion of active corticosterone and inert 11-dehydrocorticosterone. Short-term glucocorticoid excess upregulates 11beta-HSD-1 in liver and hippocampus leading to suggestions that 11beta-HSD-1 ameliorates the deleterious effects of glucocorticoid excess by its 11beta-dehydrogenase activity. However the predominant activity of 11beta-HSD-1 in vivo is 11beta-reduction, thus generating active glucocorticoid. We have re-examined the time-course of glucocorticoid regulation of 11beta-HSD-1 in the liver, hippocampus and kidney of adult male rats in vivo. Sham operation markedly reduced 11beta-HSD-1 mRNA expression in all tissues, and reduced 11beta-HSD bioactivity in liver and hippocampus when compared to untouched controls. Adrenalectomy reduced 11beta-HSD-1 expression in all tissues in the short-term (7 days), followed by subsequent recovery of enzyme activity by 21 days in liver and hippocampus. Dexamethasone replacement of adrenalectomised rats attenuated the initial decrease in hepatic 11beta-HSD-1 activity, but by 21 days dexamethasone reduced activity compared to control levels. Thus glucocorticoids regulate 11beta-HSD-1 in a complex tissue- and temporal-specific manner. This pattern of regulation suggests glucocorticoids repress 11beta-HSD-1 at least in the liver, a pattern of regulation more consistent with the evidence that 11beta-HSD-1 is an 11beta-reductase in vivo. Operational stress per se down-regulates 11beta-HSD-1 which has implications for interpretation and design of in vivo studies of 11beta-HSD-1.

Urocortin 2 modulates glucose utilization and insulin sensitivity in skeletal muscle

Skeletal muscle is the principal tissue responsible for insulin-stimulated glucose disposal and is a major site of peripheral insulin resistance. Urocortin 2 (Ucn 2), a member of the corticotropin-releasing factor (CRF) family, and its cognate type 2 CRF receptor (CRFR2) are highly expressed in skeletal muscle. To determine the physiological role of Ucn 2, we generated mice that are deficient in this peptide. Using glucose-tolerance tests (GTTs), insulin-tolerance tests (ITTs), and hyperinsulinemic euglycemic glucose clamp studies, we demonstrated that mice lacking Ucn 2 exhibited increased insulin sensitivity and were protected against fat-induced insulin resistance. Administration of synthetic Ucn 2 to mutant mice before the GTTs and ITTs restored blood glucose to WT levels. Administration of a CRFR2 selective antagonist to WT mice resulted in a GTT profile that mirrored that of Ucn 2-null mice. Body composition measurements of Ucn 2-null mice on a high-fat diet demonstrated decreases in fat and increases in lean tissue compared with WT mice. We propose that null mutant mice display increased glucose uptake in skeletal muscle through the removal of Ucn 2-mediated inhibition of insulin signaling. In keeping with these data, Ucn 2 inhibited insulin-induced Akt and ERK1/2 phosphorylation in cultured skeletal muscle cells and C2C12 myotubes. These data are consistent with the hypothesis that Ucn 2 functions as a local negative regulator of glucose uptake in skeletal muscle and encourage exploration of the possibility that suppression of the Ucn 2/CRFR2 pathway may provide benefits in insulin-resistant states such as type 2 diabetes.

Chronic Activation of Corticotropin-Releasing Factor Type 2 Receptors Reveals a Key Role for 5-HT1A Receptor Responsiveness in Mediating Behavioral and Serotonergic Responses to Stressful Challenge

Background The corticotropin-releasing factor type 2 receptor (CRFR2) is suggested to play an important role in aiding recovery from acute stress, but any chronic effects of CRFR2 activation are unknown. CRFR2 in the midbrain raphé nuclei modulate serotonergic activity of this key source of serotonin (5-HT) forebrain innervation. Methods Transgenic mice overexpressing the highly specific CRFR2 ligand urocortin 3 (UCN3OE) were analyzed for stress-related behaviors and hypothalamic-pituitary-adrenal axis responses. Responses to 5-HT receptor agonist challenge were assessed by local cerebral glucose utilization, while 5-HT and 5-hydroxyindoleacetic acid content were quantified in limbic brain regions. Results Mice overexpressing urocortin 3 exhibited increased stress-related behaviors under basal conditions and impaired retention of spatial memory compared with control mice. Following acute stress, unlike control mice, they exhibited no further increase in these stress-related behaviors and showed an attenuated adrenocorticotropic hormone response. 5-HT and 5-hydroxyindoleacetic acid content of limbic nuclei were differentially regulated by stress in UCN3OE mice as compared with control mice. Responses to 5-HT type 1A receptor challenge were significantly and specifically reduced in UCN3OE mice. The distribution pattern of local cerebral glucose utilization and 5-HT type 1A receptor messenger RNA expression levels suggested this effect was mediated in the raphé nuclei. Conclusions Chronic activation of CRFR2 promotes an anxiety-like state, yet with attenuated behavioral and hypothalamic-pituitary-adrenal axis responses to stress. This is reminiscent of stress-related atypical psychiatric syndromes such as posttraumatic stress disorder, chronic fatigue, and chronic pain states. This new understanding indicates CRFR2 antagonism as a potential novel therapeutic target for such disorders.

Urocortin 3 transgenic mice exhibit a metabolically favourable phenotype resisting obesity and hyperglycaemia on a high-fat diet

Aims/hypothesisUrocortins are the endogenous ligands for the corticotropin-releasing factor receptor type 2 (CRFR2), which is implicated in regulating energy balance and/or glucose metabolism. We determined the effects of chronic CRFR2 activation on metabolism in vivo, by generating and phenotyping transgenic mice overproducing the specific CRFR2 ligand urocortin 3.MethodsBody composition, glucose metabolism, insulin sensitivity, energy efficiency and expression of key metabolic genes were assessed in adult male urocortin 3 transgenic mice (Ucn3+) under control conditions and following an obesogenic high-fat diet (HFD) challenge.ResultsUcn3+ mice had increased skeletal muscle mass with myocyte hypertrophy. Accelerated peripheral glucose disposal, increased respiratory exchange ratio and hypoglycaemia on fasting demonstrated increased carbohydrate metabolism. Insulin tolerance and indices of insulin-stimulated signalling were unchanged, indicating these effects were not mediated by increased insulin sensitivity. Expression of the transgene in Crfr2 (also known as Crhr2)-null mice negated key aspects of the Ucn3+ phenotype. Ucn3+ mice were protected from the HFD-induced hyperglycaemia and increased adiposity seen in control mice despite consuming more energy. Expression of uncoupling proteins 2 and 3 was higher in Ucn3+ muscle, suggesting increased catabolic processes. IGF-1 abundance was upregulated in Ucn3+ muscle, providing a potential paracrine mechanism in which urocortin 3 acts upon CRFR2 to link the altered metabolism and muscular hypertrophy observed.Conclusions/interpretationUrocortin 3 acting on CRFR2 in skeletal muscle of Ucn3+ mice results in a novel metabolically favourable phenotype, with lean body composition and protection against diet-induced obesity and hyperglycaemia. Urocortins and CRFR2 may be of interest as potential therapeutic targets for obesity.

Increased anxiety in corticotropin-releasing factor type 2 receptor-null mice requires recent acute stress exposure and is associated with dysregulated serotonergic activity in limbic brain areas

BackgroundCorticotropin-releasing factor type 2 receptors (CRFR2) are suggested to facilitate successful recovery from stress to maintain mental health. They are abundant in the midbrain raphe nuclei, where they regulate serotonergic neuronal activity and have been demonstrated to mediate behavioural consequences of stress. Here, we describe behavioural and serotonergic responses consistent with maladaptive recovery from stressful challenge in CRFR2-null mice.ResultsCRFR2-null mice showed similar anxiety levels to control mice before and immediately after acute restraint stress, and also after cessation of chronic stress. However, they showed increased anxiety by 24 hours after restraint, whether or not they had been chronically stressed.Serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) contents were quantified and the level of 5-HIAA in the caudal dorsal raphe nucleus (DRN) was increased under basal conditions in CRFR2-null mice, indicating increased 5-HT turnover. Twenty-four hours following restraint, 5-HIAA was decreased only in CRFR2-null mice, suggesting that they had not fully recovered from the challenge. In efferent limbic structures, CRFR2-null mice showed lower levels of basal 5-HT in the lateral septum and subiculum, and again showed a differential response to restraint stress from controls.Local cerebral glucose utilization (LCMRglu) revealed decreased neuronal activity in the DRN of CRFR2-null mice under basal conditions. Following 5-HT receptor agonist challenge, LCMRglu responses indicated that 5-HT1A receptor responses in the DRN were attenuated in CRFR2-null mice. However, postsynaptic 5-HT receptor responses in forebrain regions were intact.ConclusionsThese results suggest that CRFR2 are required for proper functionality of 5-HT1A receptors in the raphe nuclei, and are key to successful recovery from stress. This disrupted serotonergic function in CRFR2-null mice likely contributes to their stress-sensitive phenotype. The 5-HT content in lateral septum and subiculum was notably altered. These areas are important for anxiety, and are also implicated in reward and the pathophysiology of addiction. The role of CRFR2 in stress-related psychopathologies deserves further consideration.

Inactivation of 11β-Hydroxysteroid dehydrogenase type 1 by gene targeting in mice

11β-Hydroxysteroid dehydrogenase (11β-HSD) catalyses the inter-conversion of corticosterone and inert 11-dehydrocorticosterone. The NADP(H)-dependent type 1 isozyme is widely distributed and acts predominantly as a reductase in vivo, regenerating active glucocorticoid (1). In contrast, 11β-HSD-2 is a higher-affinity, NAD-dependent, exclusive dehydrogenase, with expression limited to mineralocorticoid target tissues (kidney, colon, parotid) and placenta (2). Gene targeting of 11β-HSD-1 was accomplished in the mouse 129/Sv embryonic stem cell line CGR 8. A chimera transmitting the mutation into the germ line was successfully obtained. Animals homozygous for the targeted allele were produced by the subsequent breeding of heterozygotes. Mice homozygous for targeted 11β-HSD–1 were viable, of normal birth weight and postnatal growth and did not have major visible abnormalities.

Urocortin 3 activates AMPK and AKT pathways and enhances glucose disposal in rat skeletal muscle.

Insulin resistance (IR) in skeletal muscle is an important component of both type 2 diabetes and the syndrome of sarcopaenic obesity, for which there are no effective therapies. Urocortins (UCNs) are not only well established as neuropeptides but also have their roles in metabolism in peripheral tissues. We have shown recently that global overexpression of UCN3 resulted in muscular hypertrophy and resistance to the adverse metabolic effects of a high-fat diet. Herein, we aimed to establish whether short-term local UCN3 expression could enhance glucose disposal and insulin signalling in skeletal muscle. UCN3 was found to be expressed in right tibialis cranialis and extensor digitorum longus muscles of rats by in vivo electrotransfer and the effects studied vs the contralateral muscles after 1 week. No increase in muscle mass was detected, but test muscles showed 19% larger muscle fibre diameter (P=0.030), associated with increased IGF1 and IGF1 receptor mRNA and increased SER256 phosphorylation of forkhead transcription factor. Glucose clearance into the test muscles after an intraperitoneal glucose load was increased by 23% (P=0.018) per unit mass, associated with increased GLUT1 (34% increase; P=0.026) and GLUT4 (48% increase; P=0.0009) proteins, and significantly increased phosphorylation of insulin receptor substrate-1, AKT, AKT substrate of 160 kDa, glycogen synthase kinase-3β, AMP-activated protein kinase and its substrate acetyl coA carboxylase. Thus, UCN3 expression enhances glucose disposal and signalling in muscle by an autocrine/paracrine mechanism that is separate from its pro-hypertrophic effects, implying that such a manipulation may have promised for the treatment of IR syndromes including sarcopaenic obesity.

Expression of urocortin peptides in canine myocardium and plasma.

Urocortin (Ucn) peptides are the endogenous ligands for the corticotropin-releasing factor type 2 receptor (CRFR2). They have potentially important roles in cardiovascular physiology in health and disease, and show promise as therapeutics for congestive heart failure. Analysis of canine heart tissue showed mRNA expression of Ucn 1, Ucn 3 and CRFR2 in all heart chambers. Immunohistochemistry also demonstrated Ucns 1 and 3 expression in cardiomyocytes. To assess the potential usefulness of circulating Ucns as markers of heart disease, plasma samples from 45 dogs with cardiac disease and 15 controls were analysed by radioimmunoassay. Both Ucns 1 and 3 were measurable but the presence of cardiac disease did not alter their concentrations. Therefore, whilst Ucns are expressed in canine myocardium (where they may play a role in the endogenous neurohumoral response to cardiac disease or failure) they do not appear to be sensitive biomarkers of cardiac disease in our canine patient population.

Expression of urocortins in canine myocardium and plasma levels in dogs with cardiac disease

1 CYTOKINEANDMATRIXMETALLOPROTEINASEEXPRESSION IN BLOOD SAMPLES OF DOGS WITH CONGESTIVE HEART FAILURE. Sonja Fonfara, Simon Tew, Peter Clegg, Joanna Dukes-McEwan. Faculty of Veterinary Science, University of Liverpool, Neston, UK. Progression of acquired cardiac diseases differs between individual dogs and breeds. Myocardial extracellular matrix (ECM) remodelling is known to play an important role in the progression of cardiac diseases and pathogenesis of heart failure (CHF), with inflammation as an important co-contributor. However, the underlying pathophysiological mechanisms are still poorly understood. Cytokine and ECM metalloproteinase-gene expression in blood samples of dogs presented in CHF (n 5 10) and in dogs with no evidence of cardiac disease (n 5 10) were analysed. mRNA of the house-keeping gene GAPDH, interleukin (IL) 1, -2, -4, -8, -10, tumour necrosis factor a (TNF), interferon g (IFN), transforming growths factor (TGF) b1 and b2 and the matrix metalloproteinases (MMP) 1, 2, 3, 9 and tissue inhibitors of metalloproteinase (TIMP) 1, 2, 3, 4 was analysed using quantitative RT-PCR. Blood from dogs with CHF had increased levels of proinflammatory cytokines (IL-1, -2, -8, IFN), MMP1, -3 and TIMP3, whereas TNF, IL-10, TGFb1, TIMP1 and TIMP2 were higher in dogs with no cardiac disease. These results suggest an inflammatory state and evidence of myocardial remodelling in dogs with CHF, whereas dogs without cardiac disease revealed predominance of cardio-protective anti-inflammatory cytokines and TIMPs. Interestingly, TNF, known to be important in cardiac remodelling, was increased in normal dogs (p 5 0.019). TIMP 3, a TNF inhibitor and regulator of resident fibroblasts, was significantly increased in dogs with CHF (p 5 0.049), which suggests possible cardioprotective function. ABSTRACT #2 CARDIAC TROPONIN-I CONCENTRATION IS ELEVATED PRE AND POST-PACING IN DOGS WITH BRADYARRHTHMIAS: IS MYOCARDITIS A POTENTIAL ETIOLOGY? DJ Trafny, MA Oyama, CA Reynolds, GE Singletary, C Wormser, GD Peddle. University of Pennsylvania, Philadelphia, PA.2 CARDIAC TROPONIN-I CONCENTRATION IS ELEVATED PRE AND POST-PACING IN DOGS WITH BRADYARRHTHMIAS: IS MYOCARDITIS A POTENTIAL ETIOLOGY? DJ Trafny, MA Oyama, CA Reynolds, GE Singletary, C Wormser, GD Peddle. University of Pennsylvania, Philadelphia, PA. Bradyarrhythmias requiring permanent pacemaker implantation usually affect geriatric dogs and are often due to high-grade to complete atrioventricular block (AVB) or sick sinus syndrome (SSS). Degenerative change has been previously postulated as the likely cause of such arrhythmias, however, myocarditis has been implicated as a cause of AVB in dogs. Plasma cardiac troponin I concentration [cTnI] is a sensitive and specific marker for myocardial injury. We sought to quantify [cTnI] in dogs with bradyarrhythmias before and after artificial pacing and to correlate [cTnI] with ECG diagnosis, HR, echo parameters, serology, and outcome. Medical records were reviewed between 2006 and 2009, and [cTnI] before and after pacemaker implantation was available in 14 dogs. Additional parameters, including heart rate, serology, presence of premature beats, echo measurements, and pacing modality were recorded. The ECG diagnosis included complete AVB (n 5 9), SSS (n 5 3), high grade 2 degree AVB (n 5 1), and atrial standstill (n 5 1). Mean [cTnI] was elevated both preand post-pacing, and was significantly (P 5 0.037) higher pre-pacing (1.99 2.86mg/dL) versus post-pacing (0.24 0.29mg/dL). [cTnI] decreased in 13 of 14 (93%) dogs post-pacing, however, in only 5 of 14 (36%) patients did the [cTnI] return to the normal reference range. Seven of 14 (50%) dogs underwent serologic testing for vector-borne diseases, including Ehrlichia canis, Anaplasma phagocytophilum, Neospora caninum, Rickettsia rickettsii, Toxoplasma gondii, Borrelia burgdorferi, and Bartonella spp. Two of 7 dogs (29%) yielded weak positive titers for Borrelia burgdorferi. Four of 5 dogs (80%) yielded strong serum titers for Bartonella spp. Of the 4 dogs with positive Bartonella titers, 3 had complete AVB and 1 had atrial standstill. Six dogs underwent recheck echocardiography at the time of their post-pacing cTnI sampling and of these, 4 of 6 (67%) were found to have progressive LV enlargement and myocardial failure as compared to their pre-pacing examination. The pre-pacing [cTnI] of these 4 dogs (0.36, 4.42, 3.59 and 10.66 ng/ml) were amongst the highest pre-pacing values obtained. Nine of 14 dogs (64%) had died or were euthanized at the time of abstract preparation (median time to death or euthanasia, 263 days; range, 47–1163 days). Baseline mean [cTnI] was higher in dogs that died of cardiac disease but this difference was not significant. [cTnI] is elevated in cases of symptomatic bradyarrhythmias and does not uniformly return to normal following pacemaker implantation. Myocarditis (especially from Bartonella spp.) may be an important cause of AVB andmyocarditis in dogs. Additional prospective studies investigating Bartonella spp. and other causes of myocarditis, as well as the correlation of [cTnI] to post-pacing LV dysfunction and outcome are needed. ABSTRACT #3 DIAGNOSTIC TEST PARAMETERS IN CATS WITH HEART DISEASE AND THEIR CORRELATION WITH NT-PROANP, NT-PROBNP AND TROPONIN I MEASUREMENTS. Stephen Ettinger, DVM , Kristine Yee, DVM, Andrew Beardow, BVS, Giosi Farace, PhD, Justin Allen, DVM, Kirstie Barrett, DVM. California Animal Hospital Veterinary Specialty Group, Los Angeles, Ca. 90025. Idexx Laboratories, Westbrook, ME 04092.3 DIAGNOSTIC TEST PARAMETERS IN CATS WITH HEART DISEASE AND THEIR CORRELATION WITH NT-PROANP, NT-PROBNP AND TROPONIN I MEASUREMENTS. Stephen Ettinger, DVM , Kristine Yee, DVM, Andrew Beardow, BVS, Giosi Farace, PhD, Justin Allen, DVM, Kirstie Barrett, DVM. California Animal Hospital Veterinary Specialty Group, Los Angeles, Ca. 90025. Idexx Laboratories, Westbrook, ME 04092. 421 cats (727 samples) were presented to the California Animal Hospital Veterinary Specialty Group for evaluation of cardiac or other medical problems. All received complete cardiovascular examinations including measurement of cTnI, NT-proANP and NTproBNP. No patient preselection occurred except for recruitment of normal cats of all ages for the study. All patients received a complete physical examination; laboratory analyses included CBC, blood chemistry profile, total T4 level and urinalysis. The cardiac examination included thoracic radiography, VHSmeasurement, 2D-Doppler echocardiography and ECG. Resting blood pressures were measured when the cat was cooperative. Cardiac biomarkers were obtained from plasma samples taken at the same time as other cardiac studies were completed. The aim of this study is to determine the correlation of the above markers with physical parameters such as echo-doppler. Non-parametric linear regression analysis of the biomarkers with specific echo derived measurements showed that NTproBNP has a stronger correlation with LA/Ao than Troponin I and NTproANP (0.53, p o 0.0001 vs. 0.43, p o 0.0001 and 0.42, p o 0.0001). IVS and LVPW have similar Spearmean’s r values with NTproBNP and Troponin I. The latter is interesting since it is a marker of muscle damage rather stretch. NTproANP, another marker of stretch, has a much weaker correlation with these two measurements. This would suggest that the disease processes in the cat involve muscle damage and ventricular stretch. It would also suggest that NT-proANP may not be as useful a measure of heart size change. ABSTRACT #4 EXPRESSION OF UROCORTINS IN CANINE MYOCARDIUM AND PLASMA LEVELS IN DOGS WITH CARDIAC DISEASE. G Fraga Veloso, DG Ohad, AJ Francis, JM Vaughan, DG Brownstein, GJ Culshaw, WW Vale, AT French, PM Jamieson. Royal (Dick) School of Veterinary Studies, University of Edinburgh Hospital for Small Animals, Roslin, UK. Department of Clinical Sciences, The Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel. The Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, CA. Centre for Cardiovascular Science, The Queen’s Medical Research Institute, Edinburgh, UK.4 EXPRESSION OF UROCORTINS IN CANINE MYOCARDIUM AND PLASMA LEVELS IN DOGS WITH CARDIAC DISEASE. G Fraga Veloso, DG Ohad, AJ Francis, JM Vaughan, DG Brownstein, GJ Culshaw, WW Vale, AT French, PM Jamieson. Royal (Dick) School of Veterinary Studies, University of Edinburgh Hospital for Small Animals, Roslin, UK. Department of Clinical Sciences, The Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel. The Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, CA. Centre for Cardiovascular Science, The Queen’s Medical Research Institute, Edinburgh, UK. Urocortin peptides are the endogenous ligands for the corticotropin-releasing factor type 2 receptor (CRFR2). They have potentially important roles in cardiovascular physiology in health and disease, and show promise as therapeutics for congestive cardiac failure. Differences in the expression of urocortins and CRFR2 receptor subtype between rodent and human heart have been observed; however no studies have been performed in the dog. 671 2010 ACVIM Forum Abstracts