THE BETA-ADRENOCEPTORS AND CATECHOLAMINE LEVELS IN LEAD POISONED RATS

To investigate beta-adrenoceptor dysfunction upon exposure to lead, we measured (a) beta-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 acet ate (2% w/v) for a period of 60 days. The radioligand [I-125]iodocyano pindolol was used for determining the density of beta-adrenoceptors in membrane fragments in vitro and a high performance liquid chromatogra phy (HPLC) for measuring plasma catecholamine levels. Plasma norepinep hrine levels were found to be significantly higher in lead-exposed rat s than in control animals (4.69 +/- 0.58 mu g/l vs. 3.67 +/- 0.53 mu g /l, p < 0.01). In lead-exposed animals the density of beta-adrenocepto rs in brain (36%), heart (68%), blood vessels (57%) and lymphocytes (4 8%) was significantly less than in controls (p < 0.001), whereas the K -d did not vary between the two groups. We have found that beta-adreno ceptor dysfunction in lead-poisoned rats was brought about by a declin e in beta-adrenoceptor density.