Effect of Diuretics on Adrenergic Receptors in the Rat

Abstract
Diuretics have been reported to alter arteriolar smooth muscle responses to adrenergic stimulation as well as lymphocyte .beta.-adrenoceptor density. We have investigated the effect of four days treatment with hydrochlorothiazide or furosemide (10 mg/kg and day) injected subcutaneously in the rat on .alpha.1-.alpha.2-and .beta.-adrenoceptors in different tissues. .alpha.1-Adrenoceptor density and affinity in whole kidney and heart ventricle as determined by 3H-prazosin binding (in the absence and presence of 10-5 M phentolamine) were unaltered by diuretic treatment, as were .beta.-adrenoceptor density and affinity in whole kidney, heart ventricle and skeletal muscle as determined by 125I-iodocyanopindolol binding (in the absence and presence of 10-7 M (-)-propranolol. The density of .alpha.2-adrenoceptors in particulate fraction from whole kidney homogenate as determined by 3H-rauwolscine binding was 12.8% higher in the hydrocholorothiazide-treated group (P < 0.05) and 15.0% higher in the furosemide-treated group (P < 0.01) than in the control group. The receptor affinity was similar in the different groups. Thus diuretic-induced alterations in adrenoceptors reported in previous studies were not observed in this study.