Effect of diuretics on adrenergic receptors in the rat

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 hydrochlorothiazide-treated group (P less than 0.05) and 15.0% higher in the furosemide-treated group (P less than 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.