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Factors released from endocardium of the ferret and pig modulate myocardial contraction

Warden-Smith, Jeremy, Shah, Ajay M. and Lewis, Malcolm John 1991. Factors released from endocardium of the ferret and pig modulate myocardial contraction. Journal of Physiology 439 , pp. 1-14.

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Abstract

1. In isolated heart muscle preparations, selective removal of the endocardium results in a characteristic and unusual negative inotropic effect. Possible mechanisms for this effect were investigated in this study. 2. In endocardium-intact preparations of ferret papillary muscle, 8-bromo-cyclic GMP, sodium nitroprusside, atrial natriuretic peptide (ANP) and substance P each induced changes in contractile behaviour similar to selective endocardial removal, and each significantly elevated myocardial cyclic GMP levels. Substance P failed to elevate myocardial cyclic GMP levels following removal of endocardium or in the presence of haemoglobin, suggesting that it may act by releasing endothelium-derived relaxing factor (EDRF) from endocardium. However, there was no change in myocardial cyclic GMP levels following endocardium removal alone. 3. In cascade bioassay experiments, it was confirmed that porcine cultured endocardial cells released an unstable humoral agent whose effects on an endothelium-denuded pig coronary artery were indistinguishable from EDRF. 4. The negative inotropic effects of endocardium removal were reversed in bioassay experiments where an endocardium-denuded papillary muscle was exposed to the effluent from a column of porcine cultured endocardial cells on microcarrier beads. This demonstrates for the first time the release of a 'contraction prolonging factor' from endocardium, the tonic release of which would explain the negative inotropic effect of endocardium removal. 5. It is concluded that elevation of ferret papillary muscle cyclic GMP (as for example with EDRF) produces changes in contractile performance similar to those induced by endocardium removal. We also demonstrate that superfused porcine cultured endocardial cells release a humoral agent (provisionally named 'endocardin') which causes reversal of the changes in mechanical properties seen after endocardial removal.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Biosciences
Medicine
Pharmacy
Subjects: R Medicine > RM Therapeutics. Pharmacology
ISSN: 0022-3751
Last Modified: 04 Jun 2017 02:12
URI: http://orca-mwe.cf.ac.uk/id/eprint/10867

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