Reduced number of digitalis receptor sites in the hypertrophied pig myocardium

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Abstract
Left ventricular hypertrophy was established in young pigs (35–40 kg) after 4 weeks of supravalvular aortic stenosis. Isolated sarcolemmal membrane fraction was characterized for specific3H-ouabain binding. Analysis revealed a single class of receptor sites of 5.7 p moles/mg protein and a dissociation constant (Kd) of the order of 6.25×10−8 M. Measurement of specific3H-ouabain binding with sarcolemmal fraction isolated from hypertrophied heart revealed a 26% reduction of digitalis receptor after 4 weeks of aortic stenosis, without any significant change in the affinity of receptor sites. This change in the number of digitalis receptors was maintained between 4 and 8 weeks of aortic stenosis and may be an important adaptive mechanism.