Change of cardiac beta-adrenoceptors in lead-exposed rats

The effect of lead on cardiac beta-adrenoceptors was studied. Wistar rats used in these trials were divided into seven groups of ten animals each (A-G). Of these, groups B was given drinking water containing 0.01% lead acetate, group C 0.05%, group D 0.1%, group E 0.5%, group F 1% and group G 2% for a period of 60 days. Group A was given pure water. A radioligand-binding assay fulfilling strict criteria of receptor affinity and density was used to quantify cardiac beta-adrenoceptors. Application of a trend test indicated that both blood and heart lead levels increased significantly from group A to group G (A < G), but that beta-adrenoceptor density decreased (G < A), whereas Kd did not vary among the seven groups. Linear regression analysis showed that decrease of cardiac beta-adrenergic receptor density was closely related to elevation of blood and heart lead levels. The results show that lead exposure results in a reduction of cardiac beta-adrenoceptor density.