Faculty Collaboration Database

Modulation of myocardial function and [Ca2+] sensitivity by moderate hypothermia in guinea pig isolated hearts. Am J Physiol 1999 Dec;277(6):H2321-32

Date

12/22/1999

Pubmed ID

10600852

DOI

10.1152/ajpheart.1999.277.6.H2321

Scopus ID

2-s2.0-0033385476 (requires institutional sign-in at Scopus site)   64 Citations

Abstract

Cardiac hypothermia alters contractility and intracellular Ca2+ concentration ([Ca2+]i) homeostasis. We examined how left ventricular pressure (LVP) is altered as a function of cytosolic [Ca2+]i over a range of extracellular CaCl2 concentration ([CaCl2]e) during perfusion of isolated, paced guinea pig hearts at 37 degrees C, 27 degrees C, and 17 degrees C. Transmural LV phasic [Ca2+] was measured using the Ca2+ indicator indo 1 and calibrated (in nM) after correction was made for autofluorescence, temperature, and noncytosolic Ca2+. Noncytosolic [Ca2+]i, cytosolic diastolic and systolic [Ca2+]i, phasic [Ca2+]i, and systolic Ca2+ released per beat (area Ca2+) were plotted as a function of 0.3-4.5 mM [CaCl2]e, and indexes of contractility [LVP, maximal rates of LVP development (+dLVP/dt) and relaxation (-dLVP/dt), and the integral of the LVP curve per beat (LVParea)] were plotted as a function of [Ca2+]i. Hypothermia increased systolic [Ca2+]i and slightly changed systolic LVP but increased diastolic LVP and [Ca2+]i. The relationship of diastolic and noncytosolic [Ca2+] to [CaCl2]e was shifted upward at 17 degrees C and 27 degrees C, whereas that of phasic [Ca2+]) to [CaCl2]e was shifted upward at 17 degrees C but not at 27 degrees C. The relationships of phasic [Ca2+]i to developed LVP, +dLVP/dt, and LVP(area) were progressively reduced by hypothermia so that maximal Ca2+-activated LVP decreased and hearts were desensitized to Ca2+. Thus mild hypothermia modestly increases diastolic and noncytosolic Ca2+ with little effect on systolic Ca2+ or released (area) Ca2+, whereas moderate hypothermia markedly increases diastolic, noncytosolic, peak systolic, and released Ca2+ and results in reduced maximal Ca2+-activated LVP and myocardial sensitivity to systolic Ca2+.

Author List

Stowe DF, Fujita S, An J, Paulsen RA, Varadarajan SG, Smart SC

MESH terms used to index this publication - Major topics in bold

Animals
Calcium
Calcium Chloride
Calibration
Coronary Circulation
Cytosol
Diastole
Fluorescent Dyes
Guinea Pigs
Heart
Heart Rate
Hypothermia, Induced
In Vitro Techniques
Indoles
Myocardial Contraction
Perfusion
Temperature
Ventricular Function, Left