PubMed Health⌕ Search

Biomedical subjects

E Guarda

Publications and source records attributed to E Guarda.

At least 37 records · Page 2Linked to original sources
PubMed1993

Endothelin receptors in cultured adult rat cardiac fibroblasts.

OBJECTIVES: Endothelins, released by vascular endothelial cells, are known growth promoters of various mesenchymal cells that contribute to stromal protein accumulation. Whether endothelins could contribute to myocardial fibrosis depends, in part on whether cardiac fibroblasts have endothelin receptors. The identification and binding characteristics of endothelin-1 and endothelin-3 and their ETA and ETB receptor subtypes in cultured adult rat cardiac fibroblasts represented study objectives. METHODS: Cultured rat cardiac fibroblasts (passages 5-10) grown until confluence were used to study radioligand binding assays, receptor subtypes, association and dissociation, effects of agonist and antagonist on binding kinetics, and affinity cross linking. RESULTS: Binding association of 125I-endothelin-1 and 125I-endothelin-3 was rapid, specific, and saturable within 60 minutes. The dissociation of receptor bound 125I-endothelin-1 was slow and partially reversible (30%-40%), suggesting more than one class of endothelin receptors, whereas the dissociation of 125I-endothelin-3 was time dependent and reversible. Competitive displacement with unlabeled endothelin-1, endothelin-3, endothelin-receptor nonselective sarafotoxin (S6b), and ETA receptor selective antagonist PED-3512-PI were used to identify receptor subtypes. Displacement of 125I-endothelin-1 by cold endothelin-1, resulted in a low affinity, high binding site (IC50 5.4 x 10(-9) M; 3.6 x 10(4) binding sites.cell-1) and a high affinity, low binding site (IC50 4.2 x 10(-4) M; 11,830 binding sites.cell-1). With 125I-endothelin-1 the IC50 s for sarafotoxin, endothelin-3, and PED-3512-PI were 1.8 x 10(-10), 1.7 x 10(-9), and 3.7 x 10(-9) M, respectively; for 125I-endothelin-3 these IC50s were 2.28 x 10(-11), 1.9 x 10(-10), and 1.7 x 10(-9) M, respectively. Endothelin receptor subunits of 53, 37, 34, and 24 kDa were identified by affinity cross linking. CONCLUSION: Endothelin-1 and endothelin-3 binding and ETA and ETB receptor subtypes are present in cardiac fibroblasts with ETB predominant. The presence of these receptors support the hypothesis that endothelins may regulate cardiac fibroblast function.

Animals↗
PubMed1993

Effects of endothelins on collagen turnover in cardiac fibroblasts.

OBJECTIVES: Endothelins (ET-1 and ET-3) may be promoters of tissue remodeling, including fibrillar collagen accumulation. The hypothesis that ET-1 and ET-3 each modify cardiac fibroblast collagen turnover was tested. METHODS: Confluent adult rat cardiac fibroblasts were maintained for 24 hours in medium with 0.4% fetal calf serum, and varying concentrations of ET-1 or ET-3. Collagen synthesis was measured by 3H-proline incorporation. The synthesis of type I and III collagens was measured by enzyme linked immunosorbent assay (ELISA). The effects of endothelins on collagenase activity were estimated by zymography. RESULTS: ET-1 and ET-3 increased collagen synthesis in a concentration-dependent manner with a maximal 1.7-fold increase (p < 0.001 v control cells). The effects of ET-1 or ET-3 on collagen synthesis were not blocked by PED-3512-PI (10(-6) M), an ETA receptor antagonist. ET-1 and ET-3 each significantly (p < 0.01) increased the synthesis of both type I and III collagens. ET-1 caused a 5.8-fold decrease in collagenase activity (p < 0.01 v control), and this effect was blocked by PED-3512-PI (10(-6) M). ET-3 did not alter collagenase activity. CONCLUSION: ET-1 and ET-3 increased the synthesis of type I and III collagens, whereas ET-1, but not ET-3, reduced collagenase activity. The effects of endothelins on collagen synthesis in cardiac fibroblasts seem to be mediated through ETA and ETB receptors, whereas their effects on collagenase seem to be mediated by ETA receptors.

Animals↗
PubMed1993

Endothelial cell induced modulation of cardiac fibroblast collagen metabolism.

OBJECTIVE: The aim was to examine the influence of vascular endothelial cells on rat cardiac fibroblast collagen synthesis and collagenase activity under co-culture conditions, and to determine whether angiotensin II or aldosterone influence endothelial cell induced modulation of fibroblast collagen metabolism. METHODS: Bovine aortic endothelial cells were grown to confluence on microporous membrane inserts and then co-cultured with cardiac fibroblasts obtained from adult rats, previously grown to confluence in 35 mm dishes supplemented with 0.4% fetal bovine serum. Collagen synthesis was measured by 3H-proline incorporation. Experiments were also conducted under similar conditions to quantitate collagenase activity by zymography in conditioned medium from fibroblasts co-cultured with endothelial cells. RESULTS: After 48 h co-culture, there was a 1.9-fold increase in fibroblast collagen synthesis when compared to fibroblasts alone (p < 0.001). Aldosterone (10(-8) M) or angiotensin II (10(-7) M) added to endothelial cells did not increase fibroblast collagen synthesis over co-cultures alone. Neither the aldosterone receptor antagonist spironolactone (10(-8) M) nor type I (DuP 753, 10(-8) M) or type II (PD 123319, 10(-8) M) angiotensin II receptor antagonists altered fibroblast collagen synthesis in co-cultures. A significant increment in collagenase activity was observed in co-cultured fibroblasts relative to collagenase activity of fibroblasts alone. CONCLUSIONS: Endothelial cells modulate both cardiac fibroblast collagen synthesis and degradation. The nature of the responsible signal(s) remains to be defined, but does not appear to be mediated or regulated by angiotensin II or aldosterone.

Aldosterone↗
PubMed1993

Changes in cyclic AMP dependent protein kinase and active stiffness in the rat volume overload model of heart hypertrophy.

OBJECTIVE: The aim was to clarify the role of cyclic AMP dependent protein kinase (PKA) and changes in mechanical heart function during development of cardiac hypertrophy induced by volume overload. METHODS: Protein and DNA contents, PKA activity, and peak systolic stress-strain relationships in hearts from animals submitted to aortocaval shunt were assessed as a function of time. Sham operated (control) rats were used as controls. RESULTS: Heart weight to body weight ratio and cardiac protein content per heart increased from d 7 (p < 0.005 and p < 0.01, respectively) reaching their highest values by d 56; the same occurred with cardiac DNA content. PKA activity.g-1 tissue in soluble extracts of hearts from rats with aortocaval shunt increased by 2.7-fold on d 2 (p < 0.005), reached a ninefold peak increase by d 7 (p < 0.0001) and declined to fourfold by d 56 with respect to control values. The end peak systolic stress-strain relation slopes were: control, 368(SEM 14) g.cm-2 (n = 16); aortocaval shunt values: 2 d, 514(28) g.cm-2 (n = 6); 7 d, 579(10) g.cm-2 (n = 7); and 56 d, 554(28) g.cm-2 (n = 7). The force generating capacity at 0% strain was also significantly higher in the shunt groups as compared to sham operated controls (p < 0.01). Early activation of PKA was also confirmed through endogenous cardiac protein phosphorylation. SDS-PAGE gel electrophoretogram and autoradiography showed more heavily phosphorylated bands in aortocaval shunt hearts than in the control group. CONCLUSIONS: PKA activity and the slope of systolic stress-strain regression line followed a similar trend throughout the study, with an early increase in both variables by d 2 in the shunt group, reaching a peak at d 7, and decreasing thereafter but remaining higher than in controls. PKA activity appears to be related to increased force generating capacity rather than to hypertrophy or increased cardiac protein content. Thus PKA activation is an early biochemical event after aortocaval shunt, followed later by cardiac hypertrophy. Changes in PKA activity showed a similar trend to mechanical heart function over time. These findings help to explain the changes in the mechanical properties of the heart preceding the development of cardiac hypertrophy in the rat model of volume overload.

Animals↗
PubMed1993

Changes in beta-adrenergic receptors of rat heart and adipocytes during volume-overload induced cardiac hypertrophy.

Modification of cardiac beta-adrenergic receptors (beta-AR), resulting from the stimulation of the sympathetic nervous system, is one of the most important factors in the generation of cardiac hypertrophy and heart failure. In this research, we propose the utilization of adipocytes as an alternative to the use of predominantly beta 2-AR subtype containing circulating lymphocytes for the convenient assessment of cardiac failure in the experimentally, volume-overload induced heart hypertrophy in rats. Using this model, we measured beta-AR both in the heart and adipocytes of male rats 2, 7, 21 and 56 days after creating an aorta-cava fistula. Whereas an increase (58%) in cardiac beta-AR density from day 7 to 21 was followed by a decrease in this measurement (30%) on day 56 [changes expressed as percentage of controls; no significant changes in beta-AR affinity (Kd) were recorded at any of the time interval studied], adipocytes beta-AR density showed a progressive increase starting on day 21 (87%) which continued until the end (131%) of the study period. This lack of correlation of the beta-AR population in both tissues supports the need for a specific evaluation of the beta 1-AR subtype in the heart and adipocyte in order to evaluate the usefulness of adipocyte cells as an alternative to assess cardiac failure.

Adipose Tissue↗
PubMed1992

Pathologic hypertrophy with fibrosis: the structural basis for myocardial failure.

The major risk factor associated with the appearance of adverse cardiovascular events and outcome attributable to cardiovascular disease is left ventricular hypertrophy (LVH). Why this should be so resides not in the increase in myocardial mass per se, but in the disruption of myocardial structure. An abnormal accumulation of fibrillar collagen within the adventitia of intramyocardial coronary arteries and neighboring interstitial spaces represents such a distortion in structure. Furthermore, this fibrosis disrupts the electrical and mechanical behavior of the hypertrophied myocardium. Mechanisms responsible for fibrillar collagen accumulation have been examined in intact animals and cultured cardiac fibroblasts. In vivo studies indicate that myocardial fibrosis is associated with the presence of chronic mineralocorticoid excess, relative to sodium intake and excretion, not hemodynamic workload. Accordingly, fibrosis can appear in both the hypertensive, hypertrophied and nonhypertensive, nonhypertrophied ventricles. In both primary and secondary hyperaldosteronism it was possible to prevent myocardial fibrosis with an aldosterone receptor antagonist, while in unilateral renal ischemia angiotensin converting enzyme (ACE) inhibition was similarly cardioprotective. A regression in fibrous tissue and normalization of diastolic stiffness has also been possible using ACE inhibition, bringing forward the concept of cardioreparation and the notion that heart failure due to fibrosis may be reversible. In vitro studies indicate that effector hormones of the renin-angiotensin-aldosterone system stimulate fibroblast collagen synthesis. Aldosterone, in pathophysiologic concentrations, and angiotensin II, in much larger concentrations, each enhance collagen synthesis without altering the mitogenic potential of these cells. Thus, elevations in circulating aldosterone and angiotensin II, relative to sodium intake, have the potential to not only alter sodium homeostasis and vascular tonicity, but also the structure of cardiovascular tissue. Thus, myocardial fibrosis represents a structural basis for pathologic hypertrophy and ultimately accounts for the appearance of adverse cardiovascular events and outcomes.

Animals↗
PubMed1992

[Evaluation of the effect of enalapril, a converting enzyme inhibitor, on lymphocytic beta-adrenergic receptors of patients with chronic cardiac insufficiency].

We have previously corroborated that lymphocyte beta-adrenergic receptor density is significantly reduced in patients with chronic heart failure. It is well known that angiotensin converting enzyme inhibitors normalize the function of sympathetic nervous system. We have assessed the effect of enalapril on lymphocyte beta-adrenergic receptor system from patients with chronic heart failure (n = 14) using a random, cross and double blind protocol. Our results show that the improvement in clinical score and ventricular function were not related with changes in the number and affinity of beta-adrenergic receptor nor cyclic AMP content in lymphocytes obtained from these patients.

Adult↗
PubMed1991

[Pepsanurin in congestive heart failure].

We have identified a plasmatic substance, "pepsanurin" (PU) obtained by pepsin hydrolysis which inhibits the renal effects of the atrial natriuretic factor (ANF). To investigate whether patients with congestive heart failure (CHF) have increased plasma levels of PU we prepared PU from 10 patients with CHF class IV (NYHA), 9 patients with CHF class II or III and 16 healthy controls. Anesthetized rats were used to test the effects of ANF, 0.5 ug/100 g body weight i.v., before and following the intraperitoneal injection of 0.5 ml of PU. The inhibition of the diuretic and natriuretic effects of ANF was 40.9 +/- 11.9% and 49.8 +/- 12% respectively for control subjects. Corresponding figures for class IV CHF patients were 62.3 +/- 3.1% and 73.8 +/- 3.5% (p less than 0.02) and for class II-III patients 39.2 +/- 7.0% and 53.1 +/- 8.2% (NS). Accordingly, an increased capacity to generate PU may underlie the decreased sensitivity to ANF in patients with advanced CHF.

Adult↗
PubMed1990

[Beta adrenergic receptors in circulating lymphocytes of patients with chronic heart failure].

Severe decompensated chronic heart failure is associated to increased levels of circulating catecholamines and decreased density of myocardial beta-adrenergic receptors. In 14 patients with stable, class II-III heart failure we studied circulating lymphocytes to determine the number of beta adrenergic receptors, the dissociation constant of 3H dihydroalprenolol (kd) and the intracellular content of cyclic AMP (AMPc). Results (mean +/- SEM) were compared to those obtained in 10 healthy controls. The number of beta receptors was significantly decreased (105 +/- 16 vs 185 +/- 24, fmol/mg of membrane protein, p less than 0.01). No differences were found in Kd (1.65 +/- 0.2 vs. 1.36 +/- 0.28 nm) nor the level of AMPc (7.9 +/- 2.1 vs 7.1 +/- 2.9 pmol/mg protein), respectively. The decreased number of beta adrenergic receptors in the circulating lymphocytes may be related to the increased level of circulating catecholamines that have been shown to be present during exercise in these patients.

Adult↗
PubMed1990

[Combined therapy with propranolol and diltiazem in chronic exertional angina].

The effects of diltiazem, 240 mg/day, were studied in 12 patients with chronic exertional angina and angiographically proven coronary artery disease, who received maintenance therapy with propranolol. Mean age was 60.1 years (range 46 to 67). Patients received propranolol, 60 to 240 mg/day, before and during the study. A double blind, placebo controlled, cross-over design was used to test the effect of added diltiazem, during 8 weeks. Duration of exercise varied from 398 +/- 30 (mean +/- SEM) to 419 +/- 37 (placebo) or 469 +/- 35 sec (diltiazem) (NS). Time to appearance of angina varied from 283 +/- 32 to 313 +/- 34 and 302 +/- 27 sec, respectively (NS). Resting and maximal effort heart rate and blood pressure did not differ among basal, placebo and diltiazem conditions. Segmental wall motion analysis by radioisotopic ventriculogram revealed dyskinetic zones during placebo or diltiazem therapy. Basal ejection fraction did not increase during exercise and this was not modified by diltiazem or placebo. Thus, the addition of diltiazem to propranolol in patients with chronic, exertional angina failed to modify angina threshold, exercise duration or left ventricular performance.

Aged↗
PubMed1989

[Acute cardiac rupture in myocardial infarction. A case report].

A 60 year old woman with a large anterior wall myocardial infarction developed severe hypotension 12 hr after admission to the coronary care unit. X rays showed an enlarged cardiac shadow and echocardiography signs of pericardial effusion. Swan Ganz catheterization revealed severe venous hypertension and no suggestion of ventricular septal rupture. Emergency surgery, initiated with partial cardiopulmonary bypass, showed a 1 cm tear of the anterior wall of the left ventricle, close to the left anterior descending artery. A successful repair was obtained by suture on teflon pledgets. After a difficult postoperative course, the patient was doing well 8 months after surgery.

Electrocardiography↗
PubMed1989

[Value of 2-dimensional echocardiography in infective endocarditis].

We analyzed the two dimensional echocardiograms (2D echo) of 41 patients with infective endocarditis (IE). The diagnosis of endocarditis was based on typical clinical findings, positive blood cultures or anatomical findings at operation or necropsy. Age ranged from 21 to 73 years. Endocarditis was localized in a native valve in 30 patients (aortic 18, mitral 11 and tricuspid 1), a biologic prosthesis in 9 (mitral 4, aortic 4, unknown 1) and a mechanical valve in 4 (aortic 3, mitral 1). The echocardiogram showed vegetations, valve rupture or abscess in 83% of IE in native valves, 56% of IE in biologic prosthesis and 25% of IE in mechanical valves (p less than 0.05, native vs prosthetic valves). The sensitivity of 2D echo was studied in 27 subjects with known anatomical findings. It was 79% for vegetations (mitral 91%, aortic 72%, NS), 53% for valve rupture (mitral 83%, aortic 33%, p less than 0.05) and 70% for abscess. Specificity was over 89% for all lesions. Systemic embolism occurred in 41% of patients with vegetations and in 25% of those without (p = 0.07).

Adult↗
PubMedDate not supplied

Effects of angiotensin II on canine and porcine coronary epicardial and resistance arteries.

Coronary resistance arteriolar diameter importantly regulates myocardial blood flow, and is influenced by circulating neurohumoral agents. Angiotensin II (A-II) is a circulating polypeptide that is chronically elevated in heart failure and serves as a potent peripheral vasoconstrictor agent. However, its effects on isolated coronary resistance arterioles is relatively unknown. We compared the vasomotor effects of A-II on coronary epicardial and resistance arterioles in vitro from both the canine and porcine heart in order to determine the effects of A-II in different vascular beds and species. Epicardial rings were studied under isometric recording conditions, while resistance arterioles (50-150 microns) were studied in vitro using a video imaging system to record diameter. A-II, whether applied to passively distended or preconstricted porcine resistance arterioles, did not cause vasoconstriction when applied as a bolus or as cumulative doses. In preconstricted canine resistance arterioles, A-II elicited dose-dependent vasodilation (EC50 = 0.2 nM). In passively distended canine arterioles, high concentrations of A-II (0.1 microM) applied as a bolus elicited transient vasoconstriction in 28% of the vessels studied. In large epicardial rings, A-II was a weak vasoconstrictor, with greater potency in canine arteries compared to porcine arteries. In canine arteries, vasoconstriction to A-II was augmented after incubation with indomethacin. In contrast to the findings in canine arteries, the A-II vasoconstrictor response in porcine coronary arteries was decreased after incubation with indomethacin or removal of the endothelium. Thus, A-II elicits the release of a vasodilator prostanoid in epicardial canine coronary arteries and a vasoconstrictor prostanoid in porcine vessels which modulate the vasomotor action of A-II.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗