Phorbol ester receptors in cardiac myocytes of salt-sensitive and salt-resistant Dahl rats.

A moderate degree of cardiac hypertrophy develops in salt-sensitive Dahl (DS) rats after 5 weeks on a high-salt (8% NaCl) diet. Cardiac hypertrophy is accompanied by a significant reduction in the number of phorbol ester receptors on enzymatically dissociated myocytes with no changes in their affinities. In contrast, the number and properties of these receptors are not influenced by variations of dietary salt intake in the salt-resistant Dahl (DR) rat. Since phorbol esters are closely related to protein kinase C, a potent stimulator of Ca2+ transport in the heart, these results suggest that loss of phorbol ester binding sites may limit the inotropic reserve of the hypertrophied myocardium.