Altered intracellular adrenoceptor distribution in myocardium of spontaneously hypertensive rats
Limas, C.J.; Limas, C.
American Journal of Physiology 253(4 Pt 2): H904-H908
1987
ISSN/ISBN: 0002-9513 PMID: 2889373 Document Number: 301605
The number of membrane-bound .beta.-adrenoceptors is reduced in the myocardium of spontaneously hypertensive rats, and this decline may account for the decreased inotropic responsiveness to .beta.-agonists. It is not known, however, whether the total complement of cellular .beta.-receptors is lower in hypertensive animals. This issue was examined using two different approaches: acid elution of cell surface-bound .beta.-receptor ligands and comparison of the number of receptors in the plasma membrane and a postcytosolic vesicular fraction. Approximately 30% of the total .beta.-receptors were located intracellularly in Wistar-Kyoto rats compared with 42% for spontaneously hypertensive rats. Similarly, a decline in membrane-bound .beta.-receptors in hypertensive rats was balanced by a rise in receptors associated with the vesicular fraction. In contrast, .alpha.1-adrenceptors were higher in the membrane and lower in the vesicular fraction of hypertensive rats without a significant difference in total .alpha.-receptors compared with normotensive animals. Differences in adrenergic responsiveness in this, and perhaps other, models of cardiac hypertrophy reflect altered intracellular distribution of adrenoceptors, which may be under the control of the sympathetic nervous system.