Peroxisome proliferators and T3 operate by way of distinct receptors.

Peroxisome proliferators and thyroid hormones have a number of common metabolic effects. The possibility that the signal transduction pathways of both groups of effectors converge at the receptor level was investigated. It was shown that T3, specifically bound to the rat thyroid beta-receptor, was not displaced to a significant extent by ciprofibrate or bezafibrate. No specific binding of T3 to the mouse peroxisome proliferator activated receptor could be demonstrated. In transactivation experiments peroxisome proliferators were unable to activate the thyroid receptor and T3 did not activate a chimeric receptor containing the ligand binding domain of the peroxisome proliferator activated receptor. It is concluded that peroxisome proliferators and thyroid hormone do not cross-react at the level of their nuclear receptors.