Protein expression studies of desmoplakin mutations in cardiomyopathy patients reveal different molecular disease mechanisms.

Mutations in the gene for desmoplakin (DSP) may cause arrhythmogenic right ventricular cardiomyopathy (ARVC) and Carvajal syndrome (CS). Desmoplakin is part of all desmosomes, which are abundantly expressed in both myocardial and epidermal tissue and serve as intercellular mechanical junctions. This study aimed to investigate protein expression in myocardial and epidermal tissue of ARVC and CS patients carrying DSP mutations in order to elucidate potential molecular disease mechanisms. Genetic investigations identified three ARVC patients carrying different heterozygous DSP mutations in addition to a homozygous DSP mutation in a CS patient. The protein expression of DSP in mutation carriers was evaluated in biopsies from myocardial and epidermal tissue by immunohistochemistry. Keratinocyte cultures were established from skin biopsies of mutation carriers and characterized by reverse transcriptase polymerase chain reaction, western blotting, and protein mass spectrometry. The results showed that the mutation carriers had abnormal DSP expression in both myocardial and epidermal tissue. The investigations revealed that the disease mechanisms varied accordingly to the specific types of DSP mutation identified and included haploinsufficiency, dominant-negative effects, or a combination hereof. Furthermore, the results suggest that the keratinocytes cultured from patients are a valuable and easily accessible resource to elucidate the effects of desmosomal gene mutations in humans.

Eosinophilic myocarditis.

Eosinophilic myocarditis is caused by activation of eosinophilic granulocytes whereby there is a release of eosinophilic granules. Quite a few of the released compounds, especially eosinophilic cationic proteins, have a tissue-damaging effect also in the myocardium. Eosinophilia may be due to hypersensitivity, parasitic infection etc. However, in hypereosinophilic syndromes and Loeffler's endomyocardial disease, the eosinophilia is"idiopathic." I believe that a clinical spectrum of the disease exists that is intimately correlated with the number of eosinophils and especially the degree of activation. When more is known about the cardiotropism of eosinophils in the various clinical settings, an important step will have been taken toward both the understanding and the treatment of this disease spectrum.

Jugular venous pooling during lowering of the head affects blood pressure of the anesthetized giraffe.

How blood flow and pressure to the giraffe's brain are regulated when drinking remains debated. We measured simultaneous blood flow, pressure, and cross-sectional area in the carotid artery and jugular vein of five anesthetized and spontaneously breathing giraffes. The giraffes were suspended in the upright position so that we could lower the head. In the upright position, mean arterial pressure (MAP) was 193 +/- 11 mmHg (mean +/- SE), carotid flow was 0.7 +/- 0.2 l/min, and carotid cross-sectional area was 0.85 +/- 0.04 cm(2). Central venous pressure (CVP) was 4 +/- 2 mmHg, jugular flow was 0.7 +/- 0.2 l/min, and jugular cross-sectional area was 0.14 +/- 0.04 cm(2) (n = 4). Carotid arterial and jugular venous pressures at head level were 118 +/- 9 and -7 +/- 4 mmHg, respectively. When the head was lowered, MAP decreased to 131 +/- 13 mmHg, while carotid cross-sectional area and flow remained unchanged. Cardiac output was reduced by 30%, CVP decreased to -1 +/- 2 mmHg (P < 0.01), and jugular flow ceased as the jugular cross-sectional area increased to 3.2 +/- 0.6 cm(2) (P < 0.01), corresponding to accumulation of approximately 1.2 l of blood in the veins. When the head was raised, the jugular veins collapsed and blood was returned to the central circulation, and CVP and cardiac output were restored. The results demonstrate that in the upright-positioned, anesthetized giraffe cerebral blood flow is governed by arterial pressure without support of a siphon mechanism and that when the head is lowered, blood accumulates in the vein, affecting MAP.

Prevalence of nocturia and fecal and urinary incontinence and the association to childhood obesity: a study of 6803 Danish school children.

INTRODUCTION: Fecal and urinary incontinence are common disorders in children. Obesity and its associated comorbidities have become increasingly common, and a relation between obesity, nocturia, incontinence, and nocturnal enuresis has been suggested. OBJECTIVE: This large scale population study aims to determine the prevalence of fecal incontinence (FI), daytime urinary incontinence (DUI), nocturnal enuresis (NE), and nocturia in children at school entry and in adolescence and to clarify whether obesity is associated to any of the aforementioned symptoms. STUDY DESIGN: First-grade children and their parents and adolescents in the seventh to ninth grades were interviewed in relation to school nurse visits. The interview included questions on whether incontinence or nocturia were experienced at least once per month. The participants' age was recorded, and weight and height were measured. Body mass index (BMI) was calculated and age standardized by the use of BMI-standard deviation score (SDS), with reference to World Health Organization normative BMI data. Obesity was defined as BMI-SDS >2. Associations between obesity and incontinence and nocturia were quantified by odds ratio (OR). RESULTS: Completed interview questionnaires and measurements were obtained from 4002 children (95.1%) in the child population and 2801 adolescents (84.4%) in the adolescent population. The mean age of children was 6.45 ± 0.39 years, and 4.4% were obese. Overall 11.2% reported FI, 21.8% DUI, 16.8% NE, and 31.4% experienced nocturia. Obesity was associated with FI in first-grade boys (OR 1.86 compared with normal weight). Mean age of adolescents was 13.9 ± 0.85 years, and 7.6% of adolescent boys and 5.5% of the girls were obese. Fecal incontinence was reported by 2.1% of the adolescents, 4.5% had DUI, 1.0% stated to have NE, and 32.3% reported nocturia. Obesity was significantly associated with nocturia in adolescents (OR 1.74-2.01). DISCUSSION: The prevalence of nocturia seems constant throughout childhood and adolescent life; this has not previously been documented. Incontinence is very common at school entry, with DUI reported more frequently than enuresis by both children and adolescents. Obesity is associated with nocturia in adolescents and FI in first-grade boys, but no significant association between obesity and NE or DUI is found. Strength of this study is the very high participation rates, but the study does not reveal information on previous treatment, subtype, or severity of symptoms. CONCLUSIONS: Incontinence is very common in children. One-third of both children and adolescents experience nocturia. Obesity is associated with FI in first-grade boys and nocturia in adolescents.

Alpha-cardiac actin is a novel disease gene in familial hypertrophic cardiomyopathy.

We identified the alpha-cardiac actin gene (ACTC) as a novel disease gene in a pedigree suffering from familial hypertrophic cardiomyopathy (FHC). Linkage analyses excluded all the previously reported FHC loci as possible disease loci in the family studied, with lod scores varying between -2.5 and -6.0. Further linkage analyses of plausible candidate genes highly expressed in the adult human heart identified ACTC as the most likely disease gene, showing a maximal lod score of 3.6. Mutation analysis of ACTC revealed an Ala295Ser mutation in exon 5 close to 2 missense mutations recently described to cause the inherited form of idiopathic dilated cardiomyopathy (IDC). ACTC is the first sarcomeric gene described in which mutations are responsible for 2 different cardiomyopathies. We hypothesize that ACTC mutations affecting sarcomere contraction lead to FHC and that mutations affecting force transmission from the sarcomere to the surrounding syncytium lead to IDC.

Leucocyte depletion attenuates the early increase in myocardial capillary permeability to small hydrophilic solutes following ischaemia and reperfusion.

OBJECTIVE: The aim was to assess the significance of polymorphonuclear leucocytes on the myocardial capillary permeability to a small hydrophilic indicator, on the vascular tone of the resistance vessels, and on contractile function following ischaemia and reperfusion. METHODS: Open chest, anaesthetised dogs were randomised to treatment with polyclonal antibody against polymorphonuclear leucocytes (anti-PMN group) or non-specific antibody (control group), and subjected to 40 min of coronary occlusion followed by 3 h of reperfusion. The capillary extraction fraction and the myocardial plasma flow rate were quantitated in vivo by intracoronary indicator bolus injection and external registration of the washout, and the capillary permeability-surface area product was calculated. Postischaemic vasodilator tone in the myocardial resistance vessels was measured by the local 133xenon washout method. RESULTS: 20 dogs were included (10 in each group), and 13 dogs completed the ischaemia-reperfusion protocol (anti-PMN group, n = 7; control group, n = 6). In the anti-PMN group, blood polymorphonuclear leucocyte counts were reduced to a minimum of 15% of pretreatment values. After ischaemia and 5 min reperfusion, the capillary extraction increased by 17% in the control group but decreased by 22% in the anti-PMN group (p < 0.05). The corresponding capillary permeability-surface area product increased by 22% in the control group, but decreased by 16% in the anti-PMN group (p < 0.05). Neither maximum myocardial plasma flow during reactive hyperaemia nor contractile function were influenced by anti-PMN treatment. CONCLUSIONS: Polymorphonuclear leucocytes appear to participate in the increase in myocardial capillary permeability observed early after reperfusion following a 40 min period of ischaemia, but do not influence postischaemic vascular tone or postischaemic contractile function. During normal physiological conditions reduction of the circulating polymorphonuclear leucocyte counts did not induce significant changes in myocardial capillary permeability.

The giraffe kidney tolerates high arterial blood pressure by high renal interstitial pressure and low glomerular filtration rate.

BACKGROUND: The tallest animal on earth, the giraffe (Giraffa camelopardalis) is endowed with a mean arterial blood pressure (MAP) twice that of other mammals. The kidneys reside at heart level and show no sign of hypertension-related damage. We hypothesized that a species-specific evolutionary adaption in the giraffe kidney allows normal for size renal haemodynamics and glomerular filtration rate (GFR) despite a MAP double that of other mammals. METHODS: Fourteen anaesthetized giraffes were instrumented with vascular and bladder catheters to measure glomerular filtration rate (GFR) and effective renal plasma flow (ERPF). Renal interstitial hydrostatic pressure (RIHP) was assessed by inserting a needle into the medullary parenchyma. Doppler ultrasound measurements provided renal artery resistive index (RI). Hormone concentrations as well as biomechanical, structural and histological characteristics of vascular and renal tissues were determined. RESULTS: GFR averaged 342 ± 99 mL min(-1) and ERPF 1252 ± 305 mL min(-1) . RIHP varied between 45 and 140 mmHg. Renal pelvic pressure was 39 ± 2 mmHg and renal venous pressure 32 ± 4 mmHg. A valve-like structure at the junction of the renal and vena cava generated a pressure drop of 12 ± 2 mmHg. RI was 0.27. The renal capsule was durable with a calculated burst pressure of 600 mmHg. Plasma renin and AngII were 2.6 ± 0.5 mIU L(-1) and 9.1 ± 1.5 pg mL(-1) respectively. CONCLUSION: In giraffes, GFR, ERPF and RI appear much lower than expected based on body mass. A strong renal capsule supports a RIHP, which is >10-fold that of other mammals effectively reducing the net filtration pressure and protecting against the high MAP.

hnRNPs H, H' and F behave differently with respect to posttranslational cleavage and subcellular localization.

hnRNPs H, H' and F belong to a subfamily of the hnRNPs sharing a high degree of sequence identity. Eukaryotic expression and specific C-terminal antibodies were used to demonstrate great variation in the intracellular fate of the proteins. hnRNPs H and H' become posttranslational cleaved into C-terminal 35 kDa proteins (H(C), H'(C)) and possibly into N-terminal 22 kDa proteins. No detectable cleavage was observed for hnRNP F. hnRNP H/H' is almost exclusively localized to the nucleus of many cell types while hnRNP F varies from a predominant nuclear localization in some cells to a predominant cytoplasmic localization in other cells. The different fates may reflect differences in functional roles that so far only have included nuclear functions. The presence of significant quantities of hnRNP F in the cytoplasm of many cells indicates that it also may have a functional role here.

Antitrophic properties of antihypertensive drugs may depend solely on their blood pressure-lowering capability. A comparative study of isradipine, hydralazine, and metoprolol.

The objective of this study was to examine the effect of antihypertensive treatment on the structure of intramyocardial resistance vessels in spontaneously hypertensive rats. The rats were divided into four groups: one was used as control and the other three were treated from the age of four to 24 weeks with isradipine, hydralazine, and metoprolol, respectively. Half of the animals in each group were examined at the end of active treatment and the rest were examined three weeks later. The rats were anesthetized and killed during constant flow perfusion with 1 percent glutaraldehyde. The media index was determined by point counting. The media indices of rats treated with isradipine and hydralazine were significantly smaller than those of age-matched spontaneously hypertensive rat controls, whereas the media indices of rats in the metoprolol group did not differ significantly. Three weeks after treatment withdrawal, the media index tended to increase in all three groups, but the values for the isradipine and hydralazine groups were still significantly reduced. Non-invasive blood pressure measurements taken at the same time demonstrated a significant blood pressure reduction in all groups, although differences within each treatment group were evident. All pressures had stabilized on the level of spontaneously hypertensive rats three weeks after withdrawal. Thus, it is evident that both isradipine and hydralazine were able to prevent hypertrophy of intramyocardial vascular structure and continue to do so even after treatment withdrawal. This finding is consistent with previous findings, suggesting a close relationship between the extent of blood pressure reduction and the degree of prevention of vascular hypertrophy.

Aggressive long-term antihypertensive therapy with pinacidil does not cause regression of cardiovascular hypertrophy in the spontaneously hypertensive rat.

After dosage titration from the age of 1 month to the age of 3 months, spontaneously hypertensive rats (SHR) were treated with pinacidil 10 mg/kg daily until the age of 6 or 12 months. Morphometric data were obtained from the treated SHR as well as from untreated age-matched SHR and normotensive Wistar-Kyoto rats (WKY) at these two developmental stages. Heart:body weight ratios and media:lumen ratios for resistance vessels were determined. Vessels obtained from the mesenteric region were investigated on a myograph. Vessels from heart, kidney and lung were investigated by morphometric analysis of histological sections, only specimens from 12-month-old rats were used. In SHR no effects of either ageing or treatment were detectable, although their blood pressure had been effectively held at normotensive levels throughout the life of the treated animals from the age of 3 months. With the exception of the media index of the pulmonary vessels, which was not statistically different from treated or control SHR, the WKY morphological parameters were significantly lower. In conclusion, pinacidil normalized blood pressure without complications, but this did not affect SHR cardiovascular structure. It is suggested that development of this strain-specific enlargement can only be modified if blood pressure is kept at hypotensive levels, or if the effect of a hitherto unidentified causative factor is antagonized by more-specific pharmacological treatment.

Relation of left ventricular function and Na,K-pump concentration in suspected idiopathic dilated cardiomyopathy.

The possible relation between Na-K-pump concentration and left ventricular (LV) function was studied in 24 patients with suspected idiopathic dilated cardiomyopathy. This was done by measurement of 3H-ouabain binding to biopsies obtained during left-sided heart catheterization. In all patients light microscopy of biopsies was compatilel with dilated cardiomyopathy. Nineteen patients had impaired LV function as defined by NYHA/WHO and a Na,K-pump concentration of 331 +/- 19 pmol/g wet weight, whereas 5 patients had normal LV function and a Na,K-pump concentration of 559 +/- 62 pmol/g wet weight (p less than 0.001). The correlation between Na,K-pump concentration and ejection fraction was highly significant n = 24, r = 0.81, p less than 0.001). There was no correlation between volume fraction of collagen tissue and Na,K-pump concentration in the biopsies (n = 24, r = -0.08, p less than 0.80), indicating that the decrease in Na,K-pump concentration with dilated cardiomyopathy is not the simple outcome of increased fibrosis in the myocardium. The results indicate that the decrease in Na,K-pump concentration may be of importance for myocardial dysfunction and suggest a simple biochemical assessment of dilated cardiomyopathy by measurement of 3H-ouabain binding.

Prevalence of the parvovirus B19 genome in endomyocardial biopsy specimens.

Although enteroviruses have long been considered the most common cause of inflammatory heart muscle diseases, parvovirus B19 (PVB19) is emerging as a new and important candidate for myocarditis and dilated cardiomyopathy with inflammation (DCMi) and without inflammation (DCM). We investigated left ventricular endomyocardial biopsy specimens from 110 patients with suspected inflammatory heart disease for the presence of PVB19, Coxsackie virus (CVB), and adenovirus (Ad2) genome by polymerase chain reaction. Diagnosis of myocarditis (36 patients), DCM (18 patients), DCMi (13 patients), and perimyocarditis (12 patients) was made by immunohistochemical and histopathological investigation of endomyocardial biopsy specimens. A control group consisting of patients with arterial hypertension was also investigated. Prevalence of the PVB19 genome in endomyocardial biopsy specimens was highest in patients with DCMi (3 of 13) and patients with myocarditis (7 of 36); in patients with DCM and perimyocarditis, prevalence was 3 of 13 and 2 of 12, respectively. In patients with resolved myocarditis, no PVB19 DNA was detected; in patients with no inflammation and controls, prevalence was only 4% and 7%, respectively. CVB-RNA was detected in endomyocardial biopsy specimens from 3 of 37 patients with myocarditis; Ad2-DNA was found in 1 patient with DCM and 1 patient with perimyocarditis. These findings suggest an association of the PVB19 genome in endomyocardial biopsy specimens of adults with the development of DCM, DCMi, and chronic myocarditis more frequently than previously expected. PVB19 should therefore be recognized as a potential cardiotropic pathogen in patients of all ages.

Extracellular deposit of the cationic proteins ECP and EPX in tissue infiltrations of eosinophils related to tissue damage.

In a series of eosinophil inflammatory states affecting various organs (heart, gut, bladder and skin) we performed an immunohistochemical study of the eosinophil cationic proteins ECP and EPX. A strong correlation was noted between the liberation of ECP and EPX and tissue necrosis in all organs. In most cases ECP and EPX were found on the same location. However, one case indicated a possible differential release. Extracellular ECP and EPX were revealed concurrently with the two polyclonal antibodies and the monoclonal EG2 antibody. The latter binds to both ECP and EPX, but only during secretion. Since EG2 does not differentiate between ECP and EPX, but only during secretion. Since EG2 does not differentiate between EXP and EPX, it is for the first time demonstrated that both cationic proteins are correlated to tissue damage. The chymotrypsin-like cationic protein (CCP), related to neutrophils, showed a low correlation with the eosinophil cationic proteins in cases of tissue damage. The hypothesis is put forward that the release of eosinophil granule proteins and especially ECP results in a non-specific tissue damage.

Sudden unexpected cardiac deaths among young Swedish orienteers--morphological changes in hearts and other organs.

During the years 1979-1992 an accumulation of sudden unexpected cardiac deaths (SUD) occurred among young Swedish orienteers. A reevaluation of material saved from 16 autopsies was undertaken. Myocarditis was most frequent. It was found in different stages in the majority of cases, indicating subacute or chronic disease with ongoing reparative processes. There were severe morphological changes in all cases. All but one showed a picture of fibrosis and unspecific hypertrophy and/or degenerative changes in myocytes. The hearts were classified into three groups (A-C), based on the morphological picture of the retrieved heart tissue and the macroscopic description. Group A comprised five cases in which areas with active myocarditis combined with areas of healing or healed myocarditis widely distributed in the left ventricle were the only morphological changes found. Group B comprised four cases demonstrating foci of myocarditis in different stages in the left ventricle and changes resembling those found in arrhythmogenic right ventricular dysplasia (ARVD), including degenerative changes with fibrosis and fatty infiltration located in either ventricle. Group C comprised the remaining seven cases. In none of the cases were coronary artery or valvular anomalies present, nor significant coronary sclerosis or changes outside the heart that could cause SUD.

Reproducibility of the acute rejection diagnosis in human cardiac allografts. The Stanford Classification and the International Grading System.

Transplantation has become an accepted treatment of many cardiac end-stage diseases. Acute cellular rejection accounts for 15% to 20% of all graft failures. The first grading system of acute cellular rejection, the Stanford Classification, was introduced in 1979, and since then many other grading systems have evolved. Most recently, the International Grading System was introduced in The Journal of Heart and Lung Transplantation. In this study the interobserver reproducibility of both the Stanford Classification and the International Grading System is evaluated using Kappa statistics. Three observers evaluated 168 endomyocardial biopsy specimens according to the Stanford Classification and 100 endomyocardial biopsy specimens according to the International Grading System. The evaluation was carried out blindly. Kappa values of 54.1% and 51.5%, respectively, were obtained, both significantly above zero but not optimal. In addition to the interobserver reproducibility analysis of the two grading systems, the International Grading System is discussed. In the original description of the grading system terms such as focal, multifocal, and aggressive infiltrates and myocyte damage and myocyte necrosis are used. These terms create some difficulties in understanding or interpreting the various grades. The main problem is to distinguish between grade 1A and grade 3A. Despite the difficulties, the grading system is easy to use, but a revision is needed.

Animal experimental implantation of an atrial septal defect occluder system.

OBJECTIVE: To establish the implantation technique for the atrial septal defect occluder system (ASDOS) device in an experimental animal model and to determine long term mechanical stability of the device and its in vivo properties in terms of biocompatibility and tissue reaction. MATERIALS AND METHODS: An atrial septal defect was created and the device implanted in 17 pigs (mean weight 30 kg). The implantation technique was refined and modified because of initial technical and anatomical complications during nine acute pilot studies. The technique proved to be feasible in eight subsequent survival studies. Four pigs were electively killed three months after implantation (group 1). The remaining four pigs were killed six months after implantation (group 2). RESULTS: Necropsy showed all devices were embedded in soft tissue three months after implantation. Microscopic examination of atrial septal tissue showed an acute granulomatous inflammatory reaction in group 1 and fibrosis in group 2. The intensity of the inflammatory reaction around the device was clearly milder in group 2, indicating a decline in the inflammatory response with time. Clinical and biochemical investigations indicated acceptable biocompatibility of the device. CONCLUSION: The implantation technique for the ASDOS device in a chronic pig model has been established. Biocompatibility of the device was acceptable.

Total disruption of left atrial myxoma causing a cerebral attack and a saddle embolus in the iliac bifurcation.

A patient with emboli in the cerebrum and in the iliac bifurcation complicating left atrial myxoma is described. The pathological features and clinical implications are discussed.

Importance of abstention from alcohol in alcoholic heart disease.

A case of alcohol-associated heart disease, presenting with congestive heart failure, was followed for 36 months. After abstinence from alcohol, fractional shortening rose from 13 to 60%. After 1 1/2 years of abstinence and normal physical capacity, the alcoholic abuse was resumed. Eleven months later, the patient was again in overt heart failure. Withdrawal of alcohol was again associated with significant clinical improvement, but despite being in functional NYHA class I, fractional shortening only increased from 14 to 29%. Endomyocardial morphology was unrelated to the severity of the disease. Alcoholic heart disease is partially reversible, but total abstinence is necessary to preserve cardiac function.

The concentration of the Na,K-pump in skeletal and heart muscle in congestive heart failure.

Na,K-ATPase (or the Na,K-pump) is essential for excitability and contractility of muscle tissue. Previous studies have shown a decrease in the concentration of this pump in endomyocardial biopsies from patients with dilated cardiomyopathy. The effect of congestive heart failure on the concentration of Na,K-ATPase in skeletal muscle was assessed in 16 patients by measurement of binding of 3H-ouabain to biopsies of the vastus lateralis muscle. Ten patients had impaired left ventricular function with an ejection fraction of 0.32 +/- 0.03 and a concentration of the Na,K-pump of 229 +/- 15 pmol/g wet weight in the skeletal muscle, whereas 6 patients had an ejection fraction of 0.66 +/- 0.05 (P less than 0.001) and a concentration of 307 +/- 17 pmol/g wet weight (P less than 0.01). In endomyocardial biopsies, the concentration of Na,K-ATPase was 340 +/- 37 and 500 +/- 39 pmol/g wet weight (P less than 0.025) in patients with impaired and normal ventricular function, respectively. There was a significant correlation between the concentration of the Na,K-pump in the biopsies of the skeletal muscle and ejection fraction, as well as between its concentration in the endomyocardial and skeletal muscular biopsies (r = 0.56, P less than 0.025 and r = 0.72, P less than 0.005, respectively). The decrease in concentration of the pump in skeletal muscle may contribute to the limitation of exercise capacity in congestive heart failure.

Species differences in expression of angiotensin II receptors and angiotensin-converting enzyme in human, canine and rat mitral valve leaflets.

In normal valvular collagen turnover in the rat, angiotensin (Ang) II and angiotensin-converting enzyme (ACE) seem to be involved. In common human and canine valvular diseases, changes in valvular collagen play a pathogenetic role and the valvular renin-angiotensin system is therefore of particular interest in these species. Healthy mitral valve leaflets and adjacent left ventricular myocardium were taken from five rats and five dogs immediately after euthanasia, and from five humans at autopsy. The valvular and myocardial Ang II receptors and ACE were detected and measured by quantitative autoradiography. In rat valves, high levels of Ang II receptors and ACE were found. In human and canine valves, insignificant levels were found. Significant myocardial levels of Ang II receptors and ACE were found only in the rat. The study demonstrated major species differences regarding the level of valvular and myocardial Ang II receptors and ACE in man, dog and rat. The lack of valvular Ang II receptors and ACE in man and dog, suggest that the renin-angiotensin system plays a minor, if any, role in the physiological valvular collagen formation in these two species. The findings in humans, however, need to be confirmed using fresh material.