Preparation of radioiodinated bambuterol hydrochloride as beta receptors imaging agent

Abstract

Bambuterol·HCl was successfully labeled with 125I via direct electrophilic substitution at ambient temperature. The effect of reaction parameters such as Bambuterol amount, CAT amount, pH of the reaction mixture, reaction temperature, and reaction time and the in vitro stability of 125I-Bambuterol·HCl were studied. The maximum yield of 125I-Bambuterol·HCl was 92.5 ± 1.9%. The yield was determined by paper electrophoresis. In vitro stability study showed that it is preferred to use the freshly prepared agent. Biodistribution studies showed high uptake of 125I-Bambuterol·HCl in liver and lungs (16 ± 0.15 and 4.3 ± 0.08% injected dose/g tissue, respectively, at 5 min post injection). The uptake in liver and lung remained high up to 1 h, as β2-receptors are located mainly at the liver and lungs (bronchial smooth muscles). The clearance of 125I-Bambuterol·HCl from mice appeared to be mainly via the renal pathway. Radioiodinated Bambuterol·HCl shows promise as novel selective β2-adrenoceptor imaging agent.