Actions of extracellular chloride ion substitution on contractility of isolated ventricular myocardium

Fry, C. H., Griffiths, H. and Hall, Sarah K. 1993. Actions of extracellular chloride ion substitution on contractility of isolated ventricular myocardium. Cardiovascular Research 27 (5) , pp. 856-860. 10.1093/cvr/27.5.856

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Abstract

Objective: Replacement of extracellular chloride ions by some other anions exerts a positive inotropic effect on isolated cardiac muscle preparations. The aim of this study was to determine whether the increase of force was mediated by an intracellular alkalosis. Methods: Isometric tension development was measured using guinea pig papillary muscles during replacement of superfusate CI−; with isethionate ions. Intracellular pH and L-type Ca2+ currents were measured in isolated myocytes using epifluorescence microscopy and a switch-clamp technique respectively. Results: Reduction of extracellular CI− increased tension, a phenomenon which was partially inhibited with the anion exchange blocker SITS. Force was also increased by reducing superfusate PCO2. Reduction of superfusate [CI−] and PCO2 both produced concentration dependent intracellular alkalosis. The relationship between the changes to tension and intracellular pH was different when either the superfusate [CI−] or PCO2 was reduced, less pronounced when the [CI−] was reduced. An increase of the L-type Ca2+ current was produced in low CI− solutions which could be attributed to the accompanying intracellular alkalosis. Conclusions: The positive inotropic effect of superfusate CI− removal can only partially be explained by intracellular alkalosis. Other, as yet unknown, changes must determine the remainder of the inotropic response.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Biosciences
Subjects:	Q Science > QR Microbiology
Publisher:	Oxford University Press
ISSN:	0008-6363
Last Modified:	04 Jun 2017 07:53
URI:	https://orca.cardiff.ac.uk/id/eprint/69546

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