The density of ryanodine receptors decreases with pressure overload-induced rat cardiac hypertrophy.

We investigate the possibility that alterations in the calcium movements of the hypertrophied rat heart might involve sarcoplasmic reticulum (SR) ryanodine receptors. A decreased receptor density was observed with severe hypertrophy (0.26 +/- 0.05 and 0.35 +/- 0.06 pmol/mg protein and 170 and 366 receptors/micron2 of SR in 50-80% hypertrophy and control, respectively); however, the total number of receptors per left ventricle was unchanged. The dissociation constant (0.7 nM) was similar in both hypertrophied and control left ventricles. Thus the decreased density of the ryanodine receptors may participate in altered calcium movements in hypertrophied rat heart.