Tumor necrosis factor-alpha: specific binding sites in rodent brain and pituitary gland

Specific binding sites for TNF-alpha in mouse and rat brain, spleen and pituitary gland have been visualized and characterized, using quantitative autoradiography. Mouse recombinant 125I-TNF-alpha has been used as a radioligand. In the spleen, TNF-alpha binding sites were highly concentrated in the white pulpe of mouse and rat spleen. The IG50, as determined by displacement of radioligand by the unlabelled peptide, was 0.3 x 10(-9) M for both species. In the mouse brain, a weak specific binding was observed on the entire surface of the brain tissue. However, none of the nervous or vascular structures were specifically labelled above this signal. No specific binding was detectable in the rat brain tissue. In sharp contrast, in the anterior lobe of the pituitary gland of both mouse and rat, high concentrations of specific binding sites were detectable. Displacement curves in the mouse pituitary gland revealed the presence of two classes of binding sites with respective IC50 values of 10(-9) and 5 x 10(-11) M. A single class of TNF binding site was demonstrated in the rat with an IC50 of 10(-9) M. The presence of TNF binding sites in the anterior pituitary gland underlines the existence of regulatory pathways between the immune and neuroendocrine system.