Pharmacologic Comparison of Clinical Neutral Endopeptidase Inhibitors in a Rat Model of Acute Secretory Diarrhea

Racecadotril (acetorphan) is a neutral endopeptidase (NEP) inhibitor with known antidiarrheal activity in animals and humans; however, in humans, it suffers from shortcomings that might be improved with newer drugs in this class that have progressed to the clinic for nonenteric disease indications. To identify potentially superior NEP inhibitors with immediate clinical utility for diarrhea treatment, we compared their efficacy and pharmacologic properties in a rat intestinal hypersecretion model. Racecadotril and seven other clinical-stage inhibitors of NEP were obtained or synthesized. Enzyme potency and specificity were compared using purified peptidases. Compounds were orally administered to rats before administration of castor oil to induce diarrhea. Stool weight was recorded over 4 hours. To assess other pharmacologic properties, select compounds were orally administered to normal or castor oil–treated rats, blood and tissue samples collected at multiple time points, and active compound concentrations determined by mass spectroscopy. NEP enzyme activity was measured in tissue homogenates. Three previously untested clinical NEP inhibitors delayed diarrhea onset and reduced total stool output, with little or no effect on intestinal motility assessed by the charcoal meal test. Each was shown to be a potent, highly specific inhibitor of NEP. Each exhibited greater suppression of NEP activity in intestinal and nonintestinal tissues than did racecadotril and sustained this inhibition longer. These results suggest that newer clinical-stage NEP inhibitors originally developed for other indications may be directly repositioned for treatment of acute secretory diarrhea and offer advantages over racecadotril, such as less frequent dosing and potentially improved efficacy.

Orally active MMP-1 sparing α-tetrahydropyranyl and α-piperidinyl sulfone matrix metalloproteinase (MMP) inhibitors with efficacy in cancer, arthritis, and cardiovascular disease

α-Sulfone-α-piperidine and α-tetrahydropyranyl hydroxamates were explored that are potent inhibitors of MMP's-2, -9, and -13 that spare MMP-1, with oral efficacy in inhibiting tumor growth in mice and left-ventricular hypertrophy in rats and in the bovine cartilage degradation ex vivo explant system. α-Piperidine 19v (SC-78080/SD-2590) was selected for development toward the initial indication of cancer, while α-piperidine and α-tetrahydropyranyl hydroxamates 19w (SC-77964) and 9i (SC-77774), respectively, were identified as backup compounds.

Investigation of aminopyridiopyrazinones as PDE5 inhibitors: Evaluation of modifications to the central ring system

Efforts to improve the potency and physical properties of the aminopyridiopyrazinone class of PDE5 inhibitors through modification of the core ring system are described. Five new ring systems are evaluated and features that impart improved potency and improved solubility are delineated.

Role of PYK2 in the development of obesity and insulin resistance

Non-receptor proline-rich tyrosine kinase-2 (PYK2), which is activated by phosphorylation of one or more of its tyrosine residues, has been implicated in the regulation of GLUT4 glucose transporter translocation and glucose transport. Some data favor a positive role of PYK2 in stimulating glucose transport, whereas other studies suggest that PYK2 may participate in the induction of insulin resistance. To ascertain the importance of PYK2 in the setting of obesity and insulin resistance, we (1) evaluated the regulation of PYK2 in mice fed a high-fat diet and (2) characterized body and glucose homeostasis in wild type (WT) and PYK2(-/-) mice on different diets. We found that both PYK2 expression and phosphorylation were significantly increased in liver and adipose tissues harvested from high-fat diet fed mice. Wild type and PYK2(-/-) mice were fed a high-fat diet for 8 weeks to induce insulin resistance/obesity. Surprisingly, in response to this diet PYK2(-/-) mice gained significantly more weight than WT mice (18.7+/-1.2g vs. 9.5+/-0.6g). Fasting serum leptin and insulin and blood glucose levels were significantly increased in high-fat diet fed mice irrespective of the presence of PYK2 protein. There was a close correlation between serum leptin and body weight. Intraperitoneal glucose tolerance tests revealed that as expected, the high-fat diet resulted in increased blood glucose levels following glucose administration in wild type mice compared to those fed normal chow. An even greater increase in blood glucose levels was observed in PYK2(-/-) mice compared to wild type mice. These results demonstrate that a lack of PYK2 exacerbates weight gain and development of glucose intolerance/insulin resistance induced by a high-fat diet, suggesting that PYK2 may play a role in slowing the development of obesity, insulin resistance, and/or frank diabetes.

Transgenic model of aldosterone-driven cardiac hypertrophy and heart failure

Aldosterone classically promotes unidirectional transepithelial sodium transport, thereby regulating blood volume and blood pressure. Recently, both clinical and experimental studies have suggested additional, direct roles for aldosterone in the cardiovascular system. To evaluate aldosterone activation of cardiomyocyte mineralocorticoid receptors, transgenic mice overexpressing 11beta-hydroxysteroid dehydrogenase type 2 in cardiomyocytes were generated using the mouse alpha-myosin heavy chain promoter. This enzyme converts glucocorticoids to receptor-inactive metabolites, allowing aldosterone occupancy of cardiomyocyte mineralocorticoid receptors. Transgenic mice were normotensive but spontaneously developed cardiac hypertrophy, fibrosis, and heart failure and died prematurely on a normal salt diet. Eplerenone, a selective aldosterone blocker, ameliorated this phenotype. These studies confirm the deleterious consequences of inappropriate activation of cardiomyocyte mineralocorticoid receptors by aldosterone and reveal a tonic inhibitory role of glucocorticoids in preventing such outcomes under physiological conditions. In addition, these data support the hypothesis that aldosterone blockade may provide additional therapeutic benefit in the treatment of heart failure.

Endothelin-1 during and after cardiopulmonary bypass: association to graft sensitivity and postoperative recovery

OBJECTIVE

Our objectives are 2-fold: (1) to serially measure the release of endothelin and graft-conduit endothelin sensitivity during and after coronary artery bypass grafting and (2) to define potential relationships of changes in endothelin levels to perioperative parameters.

METHODS

Endothelin plasma content was measured in patients (n = 105) undergoing bypass grafting from select vascular compartments before operations and at specific intervals up to 24 hours postoperatively. Endothelin sensitivity was determined in isolated internal thoracic artery segments.

RESULTS

Systemic arterial and pulmonary arterial endothelin levels were increased by approximately 50% immediately after bypass grafting and increased by another 85% during the first 24 hours postoperatively. Endothelin levels were highest in patients with prolonged ventilatory requirements and extended stays in the intensive care unit (10.2 +/- 0.8 vs 13.2 +/- 1.1 fmol/mL, P =.02, and 9.8 +/- 0.7 vs 13.9 +/- 1.2 fmol/mL, P =.01, respectively. Endothelin sensitivity of the internal thoracic artery was increased in patients requiring prolonged vasodilator support with nitroglycerin.

CONCLUSIONS

Systemic and pulmonary arterial endothelin levels remained increased for at least 24 hours postoperatively. Prolonged pharmacologic management and increased intensive care unit stay were associated with increased systemic endothelin release and heightened graft-conduit sensitivity to endothelin.

Matrix metalloproteinase expression and activity in isolated myocytes after neurohormonal stimulation

Changes in myocardial matrix metalloproteinase (MMP) activity and expression have been associated with left ventricular (LV) remodeling. A recent study demonstrated that LV myocytes synthesize and release MMPs, which suggests that LV myocytes may participate in myocardial remodeling. However, extracellular stimuli that may potentially influence LV myocyte MMP production remains to be defined. In the present study MMP activity and expression were measured in porcine LV myocyte preparations (10(5) total cells; n = 6) following incubation (6 h) with endothelin-1 (ET-1;50 pM), angiotensin II (ANG II; 1 microM), or the beta-receptor agonist isoproterenol (Iso; 10 nM). LV myocyte-conditioned media were then subjected to gelatin zymography and an MMP-2 antibody capture assay. MMP zymographic gelatinase activity and MMP-2 content were increased by over 40% in LV myocyte-conditioned media after incubation with ET-1 or ANG II (P < 0.05). Exposure to the phorbol ester phorbol 12-myristate 13-acetate (PMA; 50 ng/ml) resulted in a 30% increase in zymographic gelatinase activity and a 63% increase in MMP-2 content (P < 0.05), suggesting that protein kinase C activation may be an intracellular mechanism for MMP induction. With the use of a confocal microscopy, membrane type-1 MMP (MT1-MMP) was localized to porcine LV myocytes, and immunoblotting for MT1-MMP using LV myocyte extracts revealed that after exposure to Iso, ET-1, ANG II, or PMA (P < 0.05), MT1-MMP abundance increased over 50%. Thus stimulation of specific neurohormonal systems that are relevant to LV remodeling influences LV myocyte MMP synthesis and release.

A matrix metalloproteinase induction/activation system exists in the human left ventricular myocardium and is upregulated in heart failure

BACKGROUND

Matrix metalloproteinases (MMPs) contribute to matrix remodeling in disease states such as tumor metastases. Extracellular matrix metalloproteinase inducer (EMMPRIN) has been reported to increase MMP expression, and membrane-type MMP or MT1-MMP has been implicated to activate MMPs. The present study examined whether and to what degree EMMPRIN and MT1-MMP were expressed in human left ventricular (LV) myocardium as well as the association with MMP activity and expression in dilated cardiomyopathy (DCM).

METHODS AND RESULTS

LV myocardial zymographic MMP activity increased by >2-fold with both nonischemic DCM (n=21) and ischemic DCM (n=16) compared with normal (n=13). LV myocardial abundance of MMP-9 was increased with both forms of DCM. MMP-2 and MMP-3 were increased with nonischemic DCM. MMP-1 levels were decreased with both forms of DCM. EMMPRIN increased by >250% and MT1-MMP increased by >1000% with both forms of DCM.

CONCLUSIONS

Increased LV myocardial MMP activity and selective upregulation of MMPs with nonischemic and ischemic forms of DCM occurred. Moreover, a local MMP induction/activation system was identified in isolated normal human LV myocytes that was upregulated with DCM. The control of MMP activation and expression in the failing human LV myocardium represents a new and potentially significant therapeutic target for this disease process.

Temporal synthesis and release of endothelin within the systemic and myocardial circulation during and after cardiopulmonary bypass: relation to postoperative recovery

OBJECTIVE

To determine endothelin levels in arterial, pulmonary, and myocardial vascular compartments in patients undergoing coronary artery bypass graft surgery and to examine the influence of endothelin on postoperative recovery.

DESIGN

Prospective, clinical study.

SETTING

University hospital.

PARTICIPANTS

Fifty patients undergoing elective coronary artery bypass graft surgery.

INTERVENTIONS

Endothelin plasma content (fmol/mL) was measured in 50 patients undergoing coronary revascularization from various vascular compartments before surgery and at specific intervals up to 24 hours postoperatively.

MEASUREMENTS AND MAIN RESULTS

Myocardial endothelin gradient (coronary sinus - aorta) was calculated before cardiopulmonary bypass (CPB), at release of the aortic cross-clamp, immediately after CPB, and 0.5 hour after CPB. The requirement for inotropic therapy and duration of patient stay in the intensive care unit were determined. Systemic and pulmonary endothelin levels were increased by >80% immediately after CPB when compared with preoperative values and increased again by approximately 60% during the first 24 hours postoperatively (p < 0.05). The myocardial endothelin gradient was reversed after CPB, indicating myocardial production of endothelin (pre-CPB, -0.72+/-0.39 fmol/mL v 0.5 hour post-CPB, 0.60+/-0.49 fmol/mL; p < 0.05). Longer intensive care unit times (>28 hours) were associated with higher systemic endothelin levels when compared with shorter times (<18 hours) (16.30+/-1.33 fmol/mL v 9.81+/-1.67 fmol/mL; p < 0.05). Patients with higher endothelin levels 6 hours postoperatively had greater inotropic requirements during the intensive care unit period.

CONCLUSION

Endothelin levels after CPB remained persistently increased for at least 24 hours after surgery and were associated with increased myocardial production of endothelin. These results suggest that the increased endothelin observed in the early postoperative period may contribute to a complex recovery from coronary artery bypass graft surgery.

Selective vasopressin, angiotensin II, or dual receptor blockade with developing congestive heart failure

With developing congestive heart failure (CHF), activation of the vasopressin V(1a) and angiotensin II type 1 (AT(1)) receptors can occur. In the present study, we examined the direct effects of V(1a) receptor blockade (V(1a) block), selective AT(1) receptor blockade (AT(1) block), and dual V(1a)/AT(1) receptor blockade (dual block) with respect to left ventricular (LV) function and contractility during the progression of CHF. LV and myocyte functions were examined in pigs with pacing CHF (rapid pacing, 240 beats/min, 3 weeks, n = 10), pacing CHF with concomitant V(1a) block (SR49059, 60 mg/kg, n = 8), pacing CHF with concomitant AT(1) block (irbesartan, 30 mg/kg, n = 7), or pacing CHF with dual block (n = 7). LV end-diastolic dimension and peak wall stress were reduced in all receptor blockade groups compared with CHF values. However, LV fractional shortening was increased only in the dual block group compared with CHF values (29 +/- 3 versus 21 +/- 2, P <.05). Basal LV myocyte percent shortening increased in the dual block group compared with CHF values (3.44 +/- 0.23 versus 2.88 +/- 0.11, P <. 05). Although V(1a) or AT(1) block reduced LV loading conditions, only dual block resulted in improved LV and myocyte shortening.

Myocardial matrix degradation and metalloproteinase activation in the failing heart: a potential therapeutic target

A fundamental structural event in the progression of heart failure due to dilated cardiomyopathy is left ventricular (LV) myocardial remodeling. The matrix metalloproteinases (MMPs) are an endogenous family of enzymes which contribute to matrix remodeling in several disease states. The goal of this report is to summarize recent findings regarding the myocardial MMP system and the relation to matrix remodeling in the failing heart. In both experimental and clinical forms of dilated cardiomyopathy (DCM), increased expression of certain species of myocardial MMPs have been demonstrated. Specifically, increased myocardial levels of the gelatinase, MMP-9 has been identified in both ischemic and non-ischemic forms of human DCM. In addition, stromelysin or MMP-3 increased by over four-fold in DCM. The increased levels of MMP-3 in DCM may have particular importance since this MMP degrades a wide range of extracellular proteins and can activate other MMPs. In normal human LV myocardium, the membrane type 1 MMP (MT1-MMP) was detected. These MT-MMPs may provide important sites for local MMP activation within the myocardium. In a pacing model of LV failure, MMP expression and activity increased early and were temporally associated with LV myocardial matrix remodeling. Using a broad-spectrum pharmacological MMP inhibitor in this pacing model, the degree of LV dilation was attenuated and associated with an improvement in LV pump function. Thus, increased LV myocardial MMP expression and activity are contributory factors in the LV remodeling process in cardiomyopathic disease states. Regulation of myocardial MMP expression and activity may be an important therapeutic target for controlling myocardial matrix remodeling in the setting of developing heart failure.

Myocyte endothelin exposure during cardioplegic arrest exacerbates contractile dysfunction after reperfusion

Transient left ventricular (LV) dysfunction can occur after cardioplegic arrest. The contributory mechanisms for this phenomenon are not completely understood. We tested the hypothesis that exposure of LV myocytes to endothelin (ET) during simulated cardioplegic arrest would have direct effects on contractile processes with subsequent reperfusion. LV porcine myocytes were randomly assigned to three groups: 1) CONTROL: normothermic (37 degrees C) cell media (n = 204); 2) Cardioplegia: simulated cardioplegic arrest (K(+) 24 mEq/L, 4 degrees C x 2 h) followed by reperfusion and rewarming with cell media (n = 164); and 3) Cardioplegia/ ET: simulated cardioplegic arrest in the presence of ET (200 pM) followed by reperfusion with cell media containing ET (n = 171). Myocyte contractility was measured by computer-assisted video microscopy. In a subset of experiments, myocyte intracellular calcium was determined after Fluo-3 (Molecular Probes, Eugene, OR) loading by digital fluorescence image analysis. Myocyte shortening velocity was reduced after cardioplegic arrest compared with controls (52 +/- 2 vs 84 +/- 3 microm/s, respectively; P < 0.05) and was further reduced with cardioplegic arrest and ET exposure (43 +/- 2 microm/s, P < 0.05). Intracellular calcium was significantly increased in myocytes exposed to cardioplegia compared with normothermic control myocytes and was further augmented by cardioplegia with ET supplementation (P < 0.05). Exposure of the LV myocyte to ET during cardioplegic arrest directly contributed to contractile dysfunction after reperfusion. Moreover, alterations in intracellular calcium may play a role in potentiating the myocyte contractile dysfunction associated with ET exposure during cardioplegic arrest.

Differential effects of calcium channel antagonists in the amelioration of radial artery vasospasm

BACKGROUND

Radial artery (RA) is being used for coronary artery bypass grafting (CABG) with greater frequency. However, RA is prone to post-CABG vasospasm, which may be neurohormonally mediated. Use of the calcium channel antagonist diltiazem has been advocated as a strategy to reduce post-CABG RA vasospasm. However, whether and to what degree different calcium channel antagonists influence neurohormonally induced RA vasoconstriction remains unknown.

METHODS

RA segments were collected from patients undergoing elective CABG (n = 13), and isometric tension was examined in the presence of endothelin (10 nM) or norepinephrine (1 microM). In matched RA, endothelin- or norepinephrine-induced contractions were measured in the presence of diltiazem (277 nM), amlodipine (73 nM), or nifedipine (145 nM). These concentrations of calcium channel antagonists were based upon clinical plasma profiles.

RESULTS

Endothelin and norepinephrine caused a significant increase in RA-developed tension (0.54+/-0.1 and 0.68+/-0.1 g/mg, respectively; p<0.05). Amlodipine or nifedipine significantly reduced RA vasoconstriction in the presence of endothelin (30+/-6% and 41+/-9%, respectively; p<0.05) or norepinephrine (27+/-8% and 53+/-9%, respectively; p<0.05), whereas diltiazem did not significantly reduce RA vasoconstriction.

CONCLUSIONS

These results demonstrate that neurohormonal factors released post-CABG can cause RA vasoconstriction, and that calcium channel antagonists are not equally effective in abrogating that response. Both amlodipine and nifedipine, which have a higher degree of vascular selectivity, appear to be the most effective in reducing RA vasoconstriction.

Magnesium supplementation in the prevention of arrhythmias in pediatric patients undergoing surgery for congenital heart defects

BACKGROUND

The efficacy of magnesium in the prevention of arrhythmias in pediatric patients after heart surgery remains unknown. Therefore we prospectively examined the effect of magnesium treatment on the incidence of postoperative arrhythmias in pediatric patients undergoing surgical repair of congenital heart defects.

METHODS AND RESULTS

Twenty-eight pediatric patients undergoing heart surgery with cardiopulmonary bypass were prospectively, randomly assigned in a double-blind fashion to receive intravenous magnesium (magnesium group, n = 13; 30 mg/kg) or saline (placebo group, n = 15) immediately after cessation of cardiopulmonary bypass. Magnesium, potassium, and calcium levels were measured at defined intervals during surgery and 24 hours after surgery. Continuous electrocardiographic documentation by Holter monitor was performed for 24 hours after surgery. Magnesium levels were significantly decreased below the normal reference range for patients in the placebo group compared with the magnesium group on arrival in the intensive care unit and for 20 hours after surgery. Magnesium levels remained in the normal range for patients in the magnesium group after magnesium supplementation. In 4 patients in the placebo group (27%), junctional ectopic tachycardia developed within the initial 20 hours in the intensive care unit. No junctional ectopic tachycardia was observed in the magnesium group (P =.026).

CONCLUSIONS

Although this study was originally targeted to include 100 patients, the protocol was terminated because of the unacceptable incidence of hemodynamically significant junctional ectopic tachycardia that was present in the placebo group. Thus low magnesium levels in pediatric patients undergoing heart surgery are associated with an increased incidence of junctional ectopic tachycardia in the immediate postoperative period.

Endothelin receptor pathway in human left ventricular myocytes: relation to contractility

BACKGROUND

Increased synthesis and release of the potent bioactive peptide endothelin-1 (ET-1) occurs during and after cardiac surgery. However, the cellular and molecular basis for the effects of ET-1 on human left ventricular (LV) myocyte contractility remains unknown.

METHODS

LV myocyte contractility was examined from myocardial biopsies taken from patients (n = 30) undergoing elective coronary artery bypass. LV myocytes (n = 997, > 30/patient) were isolated using microtrituration and contractility examined by videomicroscopy at baseline and after ET-1 exposure (200 pmol/L). In additional studies, myocytes were pretreated to inhibit either protein kinase C (PKC) (chelerythrine, 1 micromol/L), the sodium/hydrogen (Na/H) exchanger (EIPA, 1 micromol/L), both PKC and the Na/H exchanger, or the ET(A) receptor (BQ-123, 1 micromol/L), followed with ET-1 exposure.

RESULTS

Basal myocyte shortening increased 37.8 +/- 6.3% with ET-1 (p < 0.05). Na/H exchanger, PKC, and dual inhibition all eliminated the effects of ET-1. Furthermore, ET(A) inhibition demonstrated that ET-1 effects on myocyte contractility were mediated through the ET(A) receptor subtype.

CONCLUSIONS

ET-1 directly influences human LV myocyte contractility, which is mediated through the ET(A) receptor and requires intracellular activation of PKC and stimulation of the Na/H exchanger.

Identification of mRNA transcripts and immunohistochemical localization of Na/H exchanger isoforms in gerbil inner ear

Recent physiological and pharmacological studies have implicated involvement of the Na/H exchanger (NHE) in regulating inner ear ion homeostasis, but the cellular distribution of this membrane transporter remains unknown. Here reverse transcription and the polymerase chain reaction (RT-PCR) were employed to screen adult gerbil inner ears for mRNA transcripts encoding the four best characterized isoforms of NHE. PCR products spanning selected segments of NHE mRNAs were cloned and sequenced. The putative housekeeping gene NHE-1 was found to be expressed and the 459 bp product shared 98.7% amino acid homology with rat sequence. NHE-2, NHE-3 and NHE-4 cDNA transcripts likewise were detected and the PCR products shared 100, 99.4 and 88.9% amino acid homology, respectively, with their rat counterparts. In addition, the cellular distribution of NHE isoforms 1 and 3 was mapped in the gerbil inner ear by immunostaining with polyclonal antisera against rat antigens. In the cochlea, the antiserum against NHE-1 reacted strongly at the basolateral membrane of strial marginal cells as well as with inner and outer hair cells and spiral ganglion neurons. Less intense staining for NHE-1 was present in subpopulations of fibrocytes in the spiral limbus and in inferior and superior areas of the spiral ligament. In the vestibular system dark and transitional cells expressed abundant NHE-1 as did hair cells and vestibular ganglia neurons. Immunostaining with the antiserum against NHE-3 was limited to the apical surface of marginal cells in the stria vascularis. Based on these data, NHE-1 likely functions primarily to maintain intracellular pH levels in cells where it is found in high abundance. NHE-3, on the other hand, possibly participates in the vectorial transcellular movement of Na+ by strial marginal cells thus helping to maintain the extremely low Na+ level in cochlear endolymph.

Neurointermediate pituitary lobe cells synthesize and release interleukin-6 in vitro: effects of lipopolysaccharide and interleukin-1 beta

The cytokine interleukin-6 (IL-6) is produced by a variety of cells, including macrophages, T-cells, and B-cells. Recent studies have confirmed a neuroendocrine role for IL-6 in the regulation of anterior pituitary (AP) hormone release. Because the neurointermediate pituitary lobe (NIL) may modulate AP hormone release, we investigated the production of IL-6 by NIL cells in vitro. NIL tissue removed from pituitary glands of male Long-Evans rats was enzymatically and mechanically dispersed, and the cells were subsequently cultured in 96-well tissue culture plates for 4-6 days in 10% serum-containing RPMI-1640. Test incubations were performed in serum-free RPMI-1640, and IL-6 concentrations were determined using the 7TD1 cell bioassay. Preliminary studies revealed a cell-dependent release of IL-6: increasing the number of NIL cells per well from 6.25 to 50 x 10(3) revealed detectable basal release of IL-6 between 25-50 x 10(3) cells/well. The endotoxin lipopolysaccharide (LPS; 100 ng/ml) and IL-1 beta (100 ng/ml) stimulated IL-6 release at 25 and 50 x 10(3) cells/well. Subsequent studies used a cell density of 50 x 10(3) cells/well and demonstrated time-dependent 3- to 6-fold inductions of IL-6 release by 100 ng/ml IL-1 beta and LPS. Concentration-response studies revealed maximal stimulation of IL-6 release by 1 ng/ml and a minimally effective concentration of 1 pg/ml for both IL-1 beta and LPS. Treatment of NIL cells with 1-10 mM (Bu)2cAMP increased IL-6 release by 7- to 14-fold. Endotoxin and IL-1 beta also enhanced the accumulation of IL-6 messenger RNA in these cells. Vasopressin and oxytocin (1 microM) inhibited LPS and IL-1 beta stimulation of IL-6 release from NIL cells, but did not inhibit IL-6 release from AP cells. Immunofluorescent dual labeling of NIL cells for flow cytometry revealed that greater than 95% of the cells did not stain for CD11b/c (common epitope found on monocytes, granulocytes, and macrophages) or CD45 (leukocyte common antigen). These results demonstrate for the first time the synthesis and release of IL-6 from cultured NIL cells. Agents that enhance IL-6 release [LPS, IL-1 beta, and (Bu)2cAMP] from other cell types also increase IL-6 release from NIL cells. Vasopressin and oxytocin inhibition of IL-6 release suggests a role for these neuropeptides in feedback inhibition in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of taurine, alpha-tocopherol, retinol, selenium, and total triglycerides and cholesterol concentrations in cats with cardiac disease and in healthy cats

Epidemiologic relations were evaluated between plasma concentrations of nutrients and cardiovascular diseases. A total of 220 cats were assessed: 144 cats with noninduced acquired heart disease and 76 clinically normal cats. Plasma was assayed for taurine, alpha-tocopherol, selenium, retinol, and total cholesterol and triglycerides concentrations. Cardiovascular disease groups included dilated cardiomyopathy (n = 53), left ventricular hypertrophy (n = 28), hyperthyroidism (n = 11), and uncertain classification (n = 52). In cats with dilated cardiomyopathy, mean plasma taurine concentration was the lowest of that in cats of any group, being only 38% of the value in healthy cats; females had less than half the mean value of males. Tocopherol concentration was 20% lower than normal, and retinol concentration was 40% higher than normal. Total cholesterol concentration was 36% lower than normal. Triglycerides concentration was higher in these cats than in any other group--twice the value recorded in healthy cats and 67% higher than that in hyperthyroid cats. In cats with hypertrophic cardiomyopathy, almost 15% had mean plasma taurine concentration < 30 mumol/L. Retinol concentration was 15% higher, and triglycerides concentration was 54% higher than normal. Approximately 27% of hyperthyroid cats had mildly decreased plasma taurine concentration. Hyperthyroid cats had the lowest tocopherol and cholesterol values; both were at least 30% lower than normal. Retinol concentration was 30% higher than normal. Approximately 14% of cats with uncertain classification had mildly decreased plasma taurine concentration. Plasma retinol and triglycerides concentrations were higher than normal in 25 and 38% of these cats, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Doxorubicin-induced cardiotoxicosis. Clinical features in 32 dogs

Clinical cardiac abnormalities developed in 32 of 175 dogs that had various malignancies and were treated with doxorubicin: 31 dogs had electrocardiographic abnormalities including arrhythmias and nonspecific alterations in the R wave, ST segment, or QRS duration and 7 dogs had congestive heart failure. All seven dogs that had congestive heart failure died within 90 days. At necropsy, 13 of 32 affected dogs had noninflammatory myocardial degeneration, myocytolysis, vacuolation, and/or fibrosis and there was intramural coronary arteriosclerosis in all 13. Five dogs with lymphosarcoma were in complete clinical remission when they died of doxorubicin-induced cardiomyopathy, but the overall survival times of the lymphosarcoma subset was nevertheless longer than in previous studies. The clinical use of doxorubicin in the dog can cause cardiotoxicosis but the therapeutic benefit appears to outweigh risks in most dogs.

Problems in veterinary ultrasonographic analysis of acquired heart disease

Echocardiography in veterinary medicine has both enhanced our ability to diagnose and treat cardiac diseases in small animals and added confusion to what we already know. Because we can actually see the heart beating and visualize blood flows within the cardiac chambers as well as measure velocities of blood flows, we have a tool that increases our non-invasive diagnostic abilities. On the other hand, the lines between different heart diseases are not always clear-cut, and the more we learn about heart disease the more we see the shades of distinction between different diseases become blurred. This chapter will look at the main abnormalities we see in veterinary medicine (mitral regurgitation, pericardial disease, and the different feline and canine cardiomyopathies) and will attempt to help the veterinary echocardiographer avoid common problems encountered in acquired heart disease as well as use echocardiographic information to gain a better understanding of the disease process occurring in animals.

Plasma taurine concentrations and M-mode echocardiographic measures in healthy cats and in cats with dilated cardiomyopathy

M-mode echocardiography was completed and plasma taurine concentrations were determined in 79 healthy cats and 77 cats with dilated cardiomyopathy (DCM). In healthy cats, a relationship was not observed between plasma taurine concentrations and any M-mode echocardiographic measurement. End-systolic and end-diastolic cardiac chamber dimensions were larger; wall thickness measures were smaller; and calculations of fractional shortening were less in cats with DCM than in healthy cats. Plasma taurine concentrations less than 30 nmol/mL were detected in 7/79 healthy cats and in 52/77 cats with DCM. Of the 52 cats with DCM and an initial plasma taurine concentration less than 30 nmol/mL, 23 died or were euthanized during the first post-treatment week, 7 were lost to further study, and 22 improved after taurine supplementation. Of the 25 cats with DCM and an initial plasma taurine concentration greater than or equal to 30 nmol/mL, 9 died or were euthanatized during the first post-treatment week, and 9 were lost to further study. Two cats did not improve, of which one died and one was euthanatized 4 to 8 weeks after initiation of taurine supplementation. Five cats with a plasma taurine concentration greater than or equal to 30 nmol/mL improved after taurine supplementation. Myocardial function subsequently deteriorated in three of these cats. Two of the three cats had signs of congestive heart failure redevelop.

Animal illness and human emotion. Cardiac disease

Cardiac disease in companion animals constitutes a significant part of veterinary medicine. Because of the nature of the problems encountered, emotional problems in the owners can be expected to arise. The major difficulty in dealing with cardiac problems in small animals arises from the uncertainty of prognosis and the frequency of sudden death. This chapter reviews the most prevalent heart diseases seen in companion animals and offers ways of explaining to clients the disease process, different treatments available (and their side effects), and more importantly, prognosis. Many problems can be avoided if good client communications are established early in the course of therapy.

Echocardiographic findings in 103 cats with hyperthyroidism

Using M-mode echocardiography, cardiac abnormalities were studied in 103 cats with untreated hyperthyroidism. In addition, follow-up echocardiography was performed on 24 of these cats to assess the long-term (4 to 21 months) effect of treatment (thyroidectomy or radioiodine) on thyrotoxic cardiac disease. The most common echocardiographic abnormality in the 103 untreated hyperthyroid cats was hypertrophy of the left ventricular caudal wall (71.9%). Hypertrophy of the interventricular septum also was documented in 39.8% of the 103 cats. Other abnormalities included high values for left atrial diameter (70.0%), aortic root diameter (18.5%), and left ventricular diameter at end diastole (45.6%). In some of these cats, indices of contractility were enhanced; in 21.4% and 14.6% of the cats, values for shortening fraction and velocity of circumferential fiber shortening, respectively, were greater than those values measured in clinically normal cats. After treatment of the hyperthyroidism, left ventricular hypertrophy resolved or improved in many of the cats, as indicated by decreases in left ventricular caudal wall and interventricular septum thicknesses. Hyperdynamic wall motion resolved in all cats after treatment, as evidenced by consistent decreases in shortening fraction and velocity of circumferential fiber shortening. Despite these improvements, some cats had one or more persistently abnormal echocardiographic values after treatment. These results suggested that in cats, hyperthyroidism commonly is associated with largely reversible cardiomyopathy. In those cats in which cardiomyopathy persists or worsens after treatment, underlying primary cardiomyopathy or thyroid hormone-induced cardiac structural damage may exist.

Efficacy and toxicity of doxorubicin and cyclophosphamide used in the treatment of selected malignant tumors in 23 cats

Twenty-three cats with malignant, nonhematopoietic tumors were treated with doxorubicin and cyclophosphamide. Fourteen cats had nonresectable tumors of the mammary gland, and nine had tumors of the oral cavity. Of the cats with mammary gland adenocarcinoma, seven cats had a partial response to treatment and seven cats had no response. Of the cats with oral tumors, one cat had a complete response, three cats had a partial response, and five cats had no response. All 23 cats are dead because of tumor progression or recurrence. Toxic effects were seen in 18 of the cats; most were transient and required no alteration in the treatment protocol. A high response rate combined with acceptable toxicity warrants further evaluation of combination doxorubicin and cyclophosphamide chemotherapy in cats with nonhematopoietic neoplasia.

Nonsurgical removal of a catheter embolus from the heart of a dog

A fragment of an 18-gauge catheter was inadvertently severed during catheterization of the cephalic vein in a 7-year-old Golden Retriever. Under fluoroscopic guidance, the fragment was retrieved successfully from the right ventricle, using a self-constructed, loop-snare catheter.

Echocardiographic reference values in healthy cats sedated with ketamine hydrochloride

An M-mode echocardiographic examination was performed in a consistent manner in 30 clinically healthy cats under light ketamine hydrochloride sedation. There was a significant linear relationship between increasing body size and increasing cardiac dimensions for several echocardiographic values. Positive correlation existed between body weight and body surface area with aortic root, left ventricular caudal wall thickness (LVCW), interventricular septal thickness (IVS), IVS/LVCW, and mean velocity of circumferential fiber shortening (Vcf); there was a negative correlation between body weight and body surface area with left ventricular ejection time (LVET). Body surface area also correlated positively with percentage of ventricular minor axis dimensional change (% delta D). Positive correlations were recorded between left ventricular end-diastolic dimension (LVEDD) and left ventricular endsystolic dimension (LVESD), LVESD and LVET, LVCW and IVS, LVET (calculated by LVCW motion) and LVET (calculated by aortic valve motion), % delta D and Vcf, heart rate and Vcf, and Vcf (calculated using aortic valve motion to compute LVET) and Vcf (using LVCW motion to compute LVET). There were negative correlations between LVEDD and % delta D, LVEDD and Vcf, LVESD and Vcf, LVET and Vcf, LVET and heart rate, LVET and % delta D. Significant differences were recorded between means of echocardiographic reference values generated in this and other studies, except for LVESD.