Isolated rabbit working heart function during progressive inhibition of myocardial SERCA activity

Elliott, E.B., Kelly, A., Smith, G.L. and Loughrey, C.M. (2012) Isolated rabbit working heart function during progressive inhibition of myocardial SERCA activity. Circulation Research, 110(12), pp. 1618-1627. (doi:10.1161/CIRCRESAHA.111.262337)

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Abstract

Rationale: The extent to which sarcoplasmic reticulum Ca2+ATPase (SERCA) activity alone determines left ventricular (LV) pump function is unknown.

Objective: To correlate SERCA activity with hemodynamic function of rabbit LV during thapsigargin perfusion.

Methods and Results: Isolated rabbit hearts were perfused in working heart configuration, and LV pump function was assessed using a pressure-volume catheter. Rapid and complete (>95%) inhibition of SERCA was associated with a moderate decrease in cardiac function (to 70%–85% of control). Further decrease in cardiac function to 50%–75% of control occurred over the next ≈30 minutes despite no detectable further inhibition of SERCA activity. Analysis of the 20 seconds prior to pump failure revealed a rapid decrease in end diastolic volume. Intermediate levels of SERCA function (≈50% of control) had only minor hemodynamic effects. Parallel experiments in field-stimulated isolated ventricular cardiomyocytes monitored intracellular Ca2+ and cell shortening. On perfusion with thapsigargin, Ca2+ transient amplitude and cell shortening fell to ≈70% of control followed by increased diastolic Ca2+ concentration and diastolic cell shortening to achieve a new steady state.

Conclusions: The relationship between SERCA activity and LV function in the rabbit is highly nonlinear. In the short term, only moderate effects on LV pump function were observed despite almost complete (>95%) reduction in SERCA activity. The terminal decline of function was associated with sudden sustained increase in diastolic tone comparable to the sustained contraction observed in isolated cardiomyocytes. Secondary increases of intracellular Ca2+ and Na+ following complete SERCA inhibition eventually limit contractile function and precipitate LV pump failure.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Smith, Professor Godfrey and Loughrey, Professor Christopher and Elliott, Dr Elspeth
Authors: Elliott, E.B., Kelly, A., Smith, G.L., and Loughrey, C.M.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
Journal Name:Circulation Research
Publisher:American Heart Association
ISSN:0009-7330
ISSN (Online):1524-4571
Published Online:03 May 2012

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