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Cardiovascular Research 1997 33(1):45-53; doi:10.1016/S0008-6363(96)00173-3
© 1997 by European Society of Cardiology
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Copyright © 1997, European Society of Cardiology

Reoxygenated effluent of Tyrode-perfused heart affects papillary muscle contraction independent of cardiac perfusion

Marieke A Dijkman*, Johannes W Heslinga, Cornelis P Allaart, Pieter Sipkema and Nico Westerhof

Laboratory for Physiology, Institute for Cardiovascular Research, ICaR-VU, Free University, Van der Boechorstraat 7, 1081 BT Amsterdam, Netherlands

Objective: We determined, via a bioassay, if inotropic factors are released in the coronary circulation of the rat heart and if changes in cardiac perfusion change papillary muscle inotropy. Methods: An isolated isometrically contracting rat papillary muscle (n = 5, acceptor) was superfused with Tyrode or with reoxygenated coronary venous effluent from an isolated isovolumically beating rat heart (donor) at 27°C, which was perfused with Tyrode according to Langendorff. The superfusion solution in the muscle bath was exchanged completely in 90 s. During coronary venous effluent superfusion, the flow of the heart (donor) was changed in steps. Results: The peak force of the papillary muscle (acceptor) was unaffected by a change from Tyrode to coronary venous effluent superfusion, but time to half relaxation (RT1/2) significantly increased by 23.0 ± 9.0% (mean ± s.d.) and positive dF/dtmax significantly decreased by 14.6 ± 4.7%. These twitch characteristics were unaffected by changes in coronary perfusion while in the heart isovolumic developed left ventricular pressure did increase with perfusion (the Gregg phenomenon). Conclusions: Factors that affect papillary muscle contractility are released into the coronary circulation, but their effect is independent of the magnitude of coronary perfusion.

KEYWORDS Bio-assay; Gregg's phenomenon; Contractile function; Rat, ventricle

* Corresponding author. Tel. +31 20 444-8110/8123; Fax +31 20 444-8255; E-mail: m.dijkman.physiol@med.vu.nl


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