Alterations of GABAB binding caused by acute and chronic lead administration

The effect of lead on GABAB binding was studied on membranes obtained from acute and chronically lead-treated rats. Acute lead treatment reduced both GABAB affinity (KD) by about 30% and density of receptor (Bmax) by about 15%. On the contrary chronic lead treatment increased receptor capacity by about 20% in spite of decreased receptor affinity by 25%. Both acute and chronic lead treatment shiffted displacement curves toward higher concentration of non-labelled compound (decreased affinity). The results show that lead can affect the GABAB binding in two ways: by reducing affinity of binding and by altering capacity of binding.