Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 356 (1997), S. 788-796 
    ISSN: 1432-1912
    Keywords: Key words 17β-Estradiol ; Action potential ; Transient ; outward currents ; Calcium current ; Rat ventricular ; myocyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study describes electrophysiological effects of estrogens in isolated male rat ventricular myocytes. According to the literature these cells do not express the nuclear estrogen receptor. Action potentials or membrane currents were recorded in the whole-cell configuration with standard techniques. Action potential durations (APD) measured at a level of 0 mV (APD 0) and –70 mV (APD –70) were prolonged by 17β-estradiol (0.5 Hz stimulation frequency, 24–26° C). Threshold concentration was 1 μmol/l. At the highest concentration used (30 μmol/l) no saturation of the response was reached and APD 0 was 162% and APD –70 was 230% of the respective control. The resting potential remained unaffected in most cells. The prolongation induced by 17β-estradiol developed rapidly and reached a steady state 10 min after start of hormone superfusion. Effects of estrogen were completely reversible during 10–15 min wash-out with hormone-free solution. The extent of prolongation (10 μmol/l 17β-estradiol) was frequency dependent. Expressed as percentage of the respective control APD 0 (or APD –70) was 115% (188%) at 0.05 Hz, 118% (163%) at 0.5 Hz and 99% (129%) at 5 Hz stimulation frequency. The response was stereoselective, because 30 μmol/l 17α-estradiol did not prolong action potentials (APD 0: 101%, APD –70: 104% of the respective control, 0.5 Hz stimulation frequency). The endogenous estrogens estrone and estriol were less effective than 17β-estradiol. With 30 μmol/l estrone (0.5 Hz stimulation frequency) APD 0 was 103% and ADP-70 148% of control and with 30 μmol/l estriol APD 0 was 135% and APD –70 137% of control. The prolongation of action potentials can be explained by inhibition of transient outward current which, in rat ventricle, is composed of fast (i to,f) and slowly (i to,s) inactivating components. At 30 μmol/l 17β-estradiol i to,f was reduced to 50% and i to,s to 43% of their maximal amplitudes. The voltage sensor of i to,f or i to,s was hardly affected. Additionally, 17β-estradiol decreased the calcium current (i Ca,L) to 76% (10 μmol/l) and 38% at 30 μmol/l. The inwardly rectifying potassium current (i K1) was reduced partly with 30 μmol/l 17β-estradiol and its amplitude was 72% of control at –90 mV (inward current flow) and 65% at –40 mV (outward current flow). These results show that 17β-estradiol is active in cardiac cells which do not express the nuclear estrogen receptor. The hormone exerts class III activity and reduces calcium inward current. These effects, however, occur in vitro with concentrations above the physiological level and therefore may be without significance in vivo.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1433-0474
    Keywords: Schlüsselwörter Multifokale atriale Tachykardie (MAT) ; Chaotische Vorhoftachykardie ; Antiarrhythmische Therapie ; Säugling ; Angeborene Herzfehler ; Key words Multifocal atrial tachycardia (MAT) ; Chaotic atrial rhythm ; Antiarrhythmic therapy ; Infancy ; Congenital heart defects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Definition: Multifocal atrial tachycardia (MAT) (also called chaotic atrial rhythm or mechanism) is a rare rhythm disturbance in infancy and childhood. It usually occurs as a sequela of chronic obstructive lung disease in adults with an incidence of about 0,5% and a high mortality rate. In infancy, the incidence has been estimated to be about 0,2%, mainly found in young infants. Diagnosis: It is characterized by an atrial frequency greater than 100 per minute, 3 or more different p-wave contours, variable PP, RR and PR-intervals, and a discrete isoelectric baseline. The origin of the arrhythmia remains unclear but atrial distension may play a significant role. Discussion: We report on the clinical course and management of two patients and also review the relevant literature.
    Notes: Zusammenfassung Definition: Die multifokale atriale Tachykardie (MAT) bzw. chaotische atriale Tachykardie oder chaotische Vorhoftachykardie ist im Kindesalter selten. Im Erwachsenenalter ist sie vorwiegend bei Patienten mit akuten oder chronischen Lungenerkrankungen beschrieben und mit einer hohen Letalität behaftet. Im Gegensatz zum Auftreten im Erwachsenenalter besitzt die MAT im Kindesalter durchweg eine gute Prognose. Diagnose: Elektrokardiographisch ist die MAT durch mindestens 3 unterschiedlich konfigurierte P-Wellen charakterisiert, die nicht der elektrischen Sinusachse entsprechen. Es besteht eine isoelektrische Linie zwischen den P-Wellen, die Vorhoffrequenz beträgt normalerweise mehr als 100 Schläge/min mit variablen P-P-, P-R- und R-R-Intervallen. Die Genese dieser Tachyarrhythmie ist unklar, eine Vorhofbelastung als Auslöser ist jedoch wahrscheinlich. Diskussion: Die möglichen Ursachen und Therapiestrategien bei chaotischer Vorhoftachykardie werden anhand zweier Kasuistiken diskutiert und eine Übersicht über die vorliegende Literatur gegeben.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...