The β-adrenoceptors and catecholamine levels in lead poisoned rats

To investigate β-adrenoceptor dysfunction upon exposure to lead, we measured (a) β-adrenoceptor density in brain, heart, blood vessels and lymphocytes and (b) plasma catecholamine levels in rats with lead poisoning. Wistar rats were given drinking water containing lead acetate (2% w/v) for a period of 60 days. The radioligand [¹²⁵I]iodocyanopindolol was used for determining the density of β-adrenoceptors in membrane fragments in vitro and a high performance liquid chromatography (HPLC) for measuring plasma catecholamine levels. Plasma norepinephrine levels were found to be significantly higher in lead-exposed rats than in control animals (4.69 ± 0.58 μg/l vs. 3.67 ± 0.53 μg/l, p < 0.01). In lead-exposed animals the density of β-adrenoceptors in brain (36%), heart (68%), blood vessels (57%) and lymphocytes (48%) was significantly less than in controls (p < 0.001), whereas the K(d) did not vary between the two groups. We have found that β-adrenoceptor dysfunction in lead-poisoned rats was brought about by a decline in β-adrenoceptor density.