Reduced number of digitalis receptor sites in the hypertrophied pig myocardium.

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 specific 3H-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 X 10(-8) M. Measurement of specific 3H-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.