Cardiac and Lymphocyte β-Adrenoceptors in Perinephritis Hypertension in the Rabbit

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Abstract
The effects of perinephritis hypertension on lymphocyte and cardiac .beta.-adenoceptors in the rabbit were examined. Hypertensive animals 8-12 weeks after surgery had an increase in cardiac weight consistent with hypertrophy compared with sham-operated age-matched controls. Specific binding of [I125] iodocyanopindolol (ICYP) to cardiac ventricular membranes was reduced in the hypertensive animals (Bmax44 .+-. 14 in hypertensives and 30 .+-. 15 fmoles/mg proteins in controls; p < 0.01). However, weight-matched ventricles from a group of older sham-operated normotensive rabbits showed a similar cardiac .beta.-receptor number to that found in the hypertensive animals. There were no changes in affinity of the ligand for the binding site. The reduction in cardiac .beta.-receptor density was not accompanied by changes in the chronotropic or blood pressure responses to isoprenaline in the conscious animal. Specific ICYP binding to lymphocyte .beta.-receptors did not differ significantly between the hypertensive and age-matched normotensive animals. Lymphocyte .beta.-adrenoceptors thus may not always reflect changes in heart .beta.-adrenoceptors, and changes in receptor density may not be directly related to blood pressure or have identifiable functional significance.