Cardiac and lymphocyte beta-adrenoceptors in perinephritis hypertension in the rabbit

The effects of perinephritis hypertension on lymphocyte and cardiac beta-adrenoceptors 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 protein in controls; p less than 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.