Document Detail


Cellular mechanisms of endotoxin-induced myocardial depression in rabbits.
MedLine Citation:
PMID:  8508524     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We investigated the mechanisms by which endotoxic shock induces intrinsic myocardial depression by studying cardiac myocytes isolated from 10 anesthetized instrumented rabbits given 172 +/- 42 (mean +/- SD) micrograms/kg IV endotoxin. Left ventricular (LV) depression developed 4 +/- 1 hours after endotoxin administration, with a 15 +/- 4% increase in LV internal end-systolic diameter, measured with sonomicrometers at a matched LV end-systolic pressure of 65 +/- 10 mm Hg. Normal LV pressure, arterial PO2, and pH were maintained to minimize confounding effects of ischemia, hypoxia, and acidosis. Cardiac myocytes from endotoxin-exposed rabbits had less unloaded cell shortening and lower peak rates of cell shortening (-dL/dt) and lengthening (+dL/dt) at [Ca2+] levels ranging from 0.5 to 16 mM when compared with myocytes isolated from normal rabbits or rabbits undergoing an identical protocol but without exposure to endotoxin. At 2 mM [Ca2+], cell shortening was depressed by approximately 25% because of a decrease in action potential duration (207 +/- 70 versus 375 +/- 64 milliseconds). In contrast, there was only mild impairment of sarcoplasmic reticulum (SR) function. When myocytes were restimulated after rest periods of 4 to 480 seconds, the decrement in cell shortening (rest decay), peak -dL/dt and peak +dL/dt, and the recovery from rest decay were similar in myocytes from endotoxin-treated and normal rabbits. There was a greater decrement in cell shortening in the second beat of postrest recovery in myocytes from endotoxin-treated rabbits than in normal myocytes. This was partly due to a 12% decrement in action potential duration with rest decay, which did not occur in normal myocytes. The SR Ca2+ content assessed by contractures in 10 mM caffeine was similar in the two groups. We conclude that endotoxic shock produces a LV depression in vivo that persists in isolated myocytes studied in vitro. This intrinsic myocardial depression is largely related to endotoxin-mediated sarcolemmal alterations, which shorten action potential duration, and is not due to alterations in SR function.
Authors:
J Hung; W Y Lew
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Circulation research     Volume:  73     ISSN:  0009-7330     ISO Abbreviation:  Circ. Res.     Publication Date:  1993 Jul 
Date Detail:
Created Date:  1993-07-12     Completed Date:  1993-07-12     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0047103     Medline TA:  Circ Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  125-34     Citation Subset:  IM    
Affiliation:
Department of Medicine, University of California, San Diego.
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MeSH Terms
Descriptor/Qualifier:
Acidosis / chemically induced,  physiopathology
Action Potentials / drug effects,  physiology
Animals
Caffeine / pharmacology
Depression, Chemical
Endotoxins
Heart / drug effects
Myocardial Contraction / drug effects,  physiology*
Myocardium / pathology
Rabbits
Sarcoplasmic Reticulum / drug effects,  physiology*
Shock, Septic / chemically induced,  physiopathology*
Ventricular Function, Left / physiology*
Chemical
Reg. No./Substance:
0/Endotoxins; 58-08-2/Caffeine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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