Document Detail

Positive staircase effect in the rat heart.
MedLine Citation:
PMID:  1119557     Owner:  NLM     Status:  MEDLINE    
The apparent lack of a positive staircase effect in ray myocardium may reflect inadequate metabolic support. Isolated rat hearts (n equals 10) were perfused at 37 degrees C with Krebs buffer containing 5 mM glucose. In 10 preparations increases in heart rate from 240 to 480/min resulted in twofold increases in left ventricular pressure and dP/dt. Pacing at a rate of 480/min resulted in mechanical deterioration of the preparation and in 50% decreases of myocardial ATP concentration within a 10-min period. Hearts of open-chest rats driven at the same rate for the same period maintained normal ATP stores. In isolated papillary muscles contracting isometrically at a rate of 30/min, peak stress 15g/mm2 (mean plus or minus SE, n equals 8) and was not changed by increasing the concentration of glucose from 5 to 30 mM. When frequency was raised from 30 to 300/min, stress declined to 5.0 plus or minus .15 g/mm2 in the presence of 5mM glucose (P smaller than .001) but increased to 8.8 plus or minus .21 g/mm2 (P smaller than 0.001) in the presence of 30 mM glucose. Thus, rat ventricular myocardium exhibits a positive staircase effect at physiological heart rates when metabolic support is adequate.
P D Henry
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  228     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1975 Feb 
Date Detail:
Created Date:  1975-06-06     Completed Date:  1975-06-06     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  360-4     Citation Subset:  IM    
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MeSH Terms
Adenosine Triphosphate / metabolism
Electric Stimulation
Glucose / metabolism
Heart / physiology*
Heart Rate*
Isoproterenol / pharmacology
Myocardium / metabolism*
Papillary Muscles / metabolism
Rats / physiology*
Stimulation, Chemical
Reg. No./Substance:
50-99-7/Glucose; 56-65-5/Adenosine Triphosphate; 7683-59-2/Isoproterenol

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

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