AJP - Heart Email Content Delivery
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Am J Physiol Heart Circ Physiol 271: H1423-H1432, 1996;
0363-6135/96 $5.00
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Nagashima, M.
Right arrow Articles by Kanno, M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Nagashima, M.
Right arrow Articles by Kanno, M.

AJP - Heart and Circulatory Physiology, Vol 271, Issue 4 1423-H1432, Copyright © 1996 by American Physiological Society

ARTICLES

Alpha 1-adrenoceptor subtypes mediating inotropic and electrophysiological effects in mammalian myocardium

M. Nagashima, Y. Hattori, Y. Akaishi, N. Tohse, I. Sakuma, A. Kitabatake and M. Kanno
Department of Pharmacology, Hokkaido University School of Medicine, Sapporo, Japan.

Stimulation of alpha 1-adrenoceptors produces a positive inotropic effect in rat and rabbit ventricular myocardium via different mechanisms, the prolongation of action potential duration (APD) exclusively in the former and an increase in myofibrillar Ca2+ sensitivity in large part in the latter. This study was designed to determine whether the two inotropic mechanisms are mediated by different alpha 1-adrenoceptor subtypes. In rat papillary muscles, the positive inotropic effect and APD prolongation induced by phenylephrine (in the presence of propranolol) were inhibited by WB-4101, but not affected by chlorethylclonidine (CEC). WB-4101, but not CEC, blocked the phenylephrine-induced inhibition of the transient outward current (Ito) in rat ventricular cells. On the other hand, WB-4101 and CEC each antagonized the positive inotropic effect of phenylephrine in rabbit papillary muscles. However, the phenylephrine-induced APD prolongation observed in rabbit papillary muscles was blocked only by WB-4101. These results indicate that the WB-4101 sensitive alpha 1-adrenoceptor subtype mediates the positive inotropism that is correlated with the APD prolongation resulting from Ito reduction, whereas the CEC-sensitive subtype mediates the positive inotropism that is probably associated with increased myofibrillar Ca2+ sensitivity. Radioligand binding studies with [3H] prazosin showed a similar ratio of alpha 1A-to alpha 1B-adrenoceptor subtypes in rat and rabbit ventricular myocardium, implying that the different degree of contribution of each action mechanism to the overall inotropic effect in the two species cannot be explained by distribution of the alpha 1-adrenoceptor subtypes.


This article has been cited by other articles:


Home page
 Circ. Res.Home page
A. D. Wickenden, P. Lee, R. Sah, Q. Huang, G. I. Fishman, and P. H. Backx
Targeted Expression of a Dominant-Negative Kv4.2 K+ Channel Subunit in the Mouse Heart
Circ. Res., November 26, 1999; 85(11): 1067 - 1076.
[Abstract] [Full Text] [PDF]

Home page
 J. Pharmacol. Exp. Ther.Home page
Y.-Y. Zhang, K.-M. Xu, and C. Han
alpha 1-Adrenoceptor Subtypes Mediating Inotropic Responses in Rat Heart
J. Pharmacol. Exp. Ther., November 1, 1999; 291(2): 829 - 836.
[Abstract] [Full Text]

Home page
 Am. J. Physiol. Heart Circ. Physiol.Home page
A. Tamada, Y. Hattori, H. Houzen, Y. Yamada, I. Sakuma, A. Kitabatake, and M. Kanno
Effects of beta -adrenoceptor stimulation on contractility, [Ca2+]i, and Ca2+ current in diabetic rat cardiomyocytes
Am J Physiol Heart Circ Physiol, June 1, 1998; 274(6): H1849 - H1857.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Visit Other APS Journals Online