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Biomedical subjects

Michael Böhm

Publications and source records attributed to Michael Böhm.

131 records · Page 8Linked to original sources

Expression and localization of P-glycoprotein in human heart: effects of cardiomyopathy.

ABC-type transport proteins, such as P-glycoprotein (P-gp), modify intracellular concentrations of many substrate compounds. They serve as functional barriers against entry of xenobiotics (e.g., in the gut or the blood-brain barrier) or contribute to drug excretion. Expression of transport proteins in the heart could be an important factor modifying cardiac concentrations of drugs known to be transported by P-gp (e.g., beta-blockers, cardiac glycosides, doxorubicin). We therefore investigated the expression and localization of P-gp in human heart. Samples from 15 human hearts (left ventricle; five non-failing, five dilated cardiomyopathy, and five ischemic cardiomyopathy) were analyzed for expression of P-gp using real-time RT-PCR, immunohistochemistry, and in situ hybridization. Immunohistochemistry revealed expression of P-gp in endothelium of both arterioles and capillaries of all heart samples. Although P-gp mRNA was detected in all samples, its expression level was significantly reduced in patients with dilated cardiomyopathy. We describe variable expression of P-gp in human heart and its localization in the endothelial wall. Thus, intracardiac concentrations of various compounds may be modified, depending on the individual P-gp level.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Safety and tolerability of eprosartan in combination with hydrochlorothiazide.

The ideal antihypertensive drug should be effective in reducing blood pressure, but have a low incidence of adverse effects. Angiotensin II receptor blockers, such as eprosartan, are as effective as ACE inhibitors in reducing blood pressure, but lack the main adverse effect of ACE inhibitors, namely cough. Eprosartan has been shown to be well tolerated with a placebo-like adverse-effect profile. When given as monotherapy it is effective in reducing blood pressure; however, some patients require additional blood pressure control, which may be provided by combination therapy. Indeed, the combination of eprosartan and the thiazide diuretic hydrochlorothiazide has been shown to be effective in further reducing blood pressure in patients not optimally responding to eprosartan monotherapy. This article reviews the safety and tolerability of eprosartan in combination with hydrochlorothiazide from 17 studies of 1899 patients with hypertension and normotensive volunteers. Of these studies, four were controlled with patients receiving a fixed-dose combination, six were long-term, open-label, and another four were controlled studies with hydrochlorothiazide being given to eprosartan non-responders. The other three studies included healthy subjects receiving the combination of eprosartan and hydrochlorothiazide. There was a high completion rate in all studies evaluated. Most of the patients receiving eprosartan 600mg in combination with hydrochlorothiazide 12.5mg daily completed the studies, which supports acceptance of this combination therapy by patients. The most frequently reported adverse events in these combination studies were headache, dizziness, myalgia, and upper respiratory tract infection in patients with hypertension. The majority of adverse events were mild to moderate in intensity, and were not considered to be related to study treatment. The adverse event that was more common in patients receiving combination therapy compared with those receiving monotherapy was dizziness. This adverse event may be due to hydrochlorothiazide as it has previously been observed in patients taking thiazide diuretics. In healthy volunteers, the most frequently reported adverse events were headache, dizziness, and upper respiratory tract infection. However, none of these adverse events were considered related to study medication. In summary, the combination of eprosartan/hydrochlorothiazide is well tolerated, both as short- and long-term therapy, with most adverse events occurring early. The most frequent adverse events were headache, dizziness, and upper respiratory infection, which would be expected based on the safety profile of each of the components. Therefore, the combination of eprosartan with hydrochlorothiazide can be effectively and safely used in patients not adequately responding to eprosartan monotherapy.

Acrylates↗

[Studies about the effects of positive inotropic and vasoactive substances]

The present study describes an in vitro method to characterize inotropic and vascular effects of compounds on isolated human cardiovascular tissues. In vitro, the positive inotropic effect in electrically driven left ventricular papillary muscle strips of nonfailing and failing human myocardium was studied and compared to experiments performed in muscle preparations of guinea pigs. In radioligand binding experiments the receptor subclasses mediating the inotropic effects were characterized. In isolated coronary or pulmonary artery rings from man the effect on vascular tone could be investigated. These data show that inotropic responses for dopamine and isoprenaline in guinea pig differ from those in the failing human myocardium. Therefore, new cardiovascular effective agents should be screened in human myocardial tissue, as experimental results from other sources may be irrelevant in this respect.

Journal Article↗

Focal parvovirus B19 myocarditis in a patient with Brugada syndrome.

The Brugada syndrome is characterized by a distinct ECG pattern consisting of ST segment elevation in the right precordial leads and right bundle branch block, a propensity for life-threatening arrhythmias, and an apparently structurally normal heart. The authors describe the case of a patient with an aborted sudden cardiac death and the typical ECG signs of Brugada syndrome. Nevertheless, magnetic resonance imaging displayed signal enhancement in the left ventricular myocardium. Additionally, histologic examination, in-situ hybridization, and PCR revealed evidence of a locally restricted inflammation due to parvovirus B19. Brugada syndrome is regarded as a primary electrical disease due to dysfunction of distinctive ion channels, but focal myocarditis may serve as a trigger for ventricular arrhythmias in this patient. Further morphologic studies will be helpful to establish the possible role of structural changes in the pathophysiology of this syndrome.

Adult↗

Beta-blocker treatment of chronic heart failure: comparison of carvedilol and metoprolol.

Beta blockers have been shown to prolong survival in chronic heart failure. It is currently a matter of debate whether any beta blocker is superior to the other in terms of improving symptoms, left ventricular function, or prognosis. A number of comparative studies have been performed with metoprolol, a beta1-selective second-generation beta blocker, and carvedilol, a nonselective and vasodilatative third-generation beta blocker. This review will focus on the different pharmacological profiles of carvedilol and metoprolol as well as on the clinical consequences derived from these differences. The results indicate that in some studies carvedilol is superior to metoprolol in improving left ventricular ejection fraction. However, because there is no conclusive evidence that carvedilol is superior to metoprolol in terms of prognosis, it is not justified to substitute metoprolol with carvedilol. Comparative data on mortality reduction are not available before termination of the Carvedilol or Metoprolol European Trial. Nevertheless, the different effects of both beta blockers on the beta-adrenergic system have an impact on tolerability and beta-adrenergic responsiveness and thus exercise tolerance in heart-failure patients.

Adrenergic beta-Antagonists↗