Kim S E, Scheffel U, Szabo Z, Burns H D, Gibson R E, Ravert H T, Mathews W B, Hamill T G, Dannals R F
Division of Nuclear Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA.
J Nucl Med. 1996 Feb;37(2):307-11.
Angiotensin II (ANG II) initiates a variety of physiological effects by binding to high affinity receptors. Two ANG II receptor subtypes, AT1 and AT2, have recently been identified. This study was undertaken to evaluate [11C]L-159,884, an AT1 subtype selective nonpeptide antagonist, as a potential PET tracer.
Carbon-11-L-159,884 was prepared by alkylation of the nor precursor with [11C]methyliodide and was studied for its in vivo binding characteristics, biodistribution and kinetics in mice. The effects of PD-123319, an AT2-selective ANGII antagonist, as well as those of alpha- and beta-adrenergic drugs on [11C]L-159,884 binding were investigated also.
Administration of the AT1 antagonists resulted in dose-dependent inhibition of [11C]L-159,884 binding in the kidneys, the organ with the highest density of AT1 receptors. Inhibition was also observed in the lungs and the heart. Adrenergic drugs did not influence [11C]L-159,884 binding to AT1 receptors. Kinetic studies showed rapid tracer uptake in the liver, kidneys, lungs and heart. Excretion of the radioactivity occurred primarily through the intestinal tract (> 20% in 90 min), with less than 8% excreted through the urine.
The results suggest that [11C]L-159,884 binds in vivo to AT1 receptors in mouse kidneys, lungs and heart. This radiotracer appears to be a promising candidate for studying ANG II receptors in vivo by PET.
