The change of beta-adrenergic system in lead-induced hypertension

Lead exposure is considered to be a risk factor of cardiovascular disease. To investigate the relationship between lead and cardiovascular disease/hypertension in lead exposure, beta-adrenergic system is explored in this study. We address three topics in this study: (a) the relationship between beta-adrenergic receptor and lead level in heart, aorta, and kidney of lead-exposed rats; (b) the relationship between beta-adrenergic receptor in heart, aorta, kidney, and blood pressure in lead-exposed rats; and (c) the change of cyclic AMP level in heart, aorta, and kidney of rats with different lead levels. Wistar rats were chronically fed with 2, 1, 0. 5, 0.1, 0.05, and 0.01% lead acetate and water for 2 months. Plasma catecholamine level was measured by high-performance liquid chromatography. Radioligand binding assay was measured by a method that fulfilled strict criteria of beta-adrenoceptor using the ligand [(125)I]iodocyanopindolol. Cyclic AMP (cAMP) level was determined by radioimmunoassay. The levels of lead were determined by electrothermal atomic absorption spectrometry. The results showed that increased plasma norepinephrine level, decreased aorta beta-adrenergic receptor and cAMP, and increased kidney beta-adrenergic receptor and cAMP contributed to the elevation of blood pressure in lead-induced hypertension. The decrement of beta-adrenoceptor and cAMP in heart resulted in decreased contractility in heart.