Effect of chemical structure of some phosphonic acids labeled with 188Re on their behavior in laboratory animals

The article considers effects of chemical structure of some phosphonic acids labeled with 188Re on their pharmacokinetic behavior in organisms of intact rats following intravenous injection. The properties of acids with two phoshonic groups - 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), four phosphonic groups - N,N,N’,N’-ethylenediaminetetrakis(methylenephosphonic acid) (EDTMP) and oxa-bis(ethylenenitrilo)tetra(methylenephosphonic acid) (OENTMP), five phosphonic groups diethylenetriaminopentakis(methylphosphonic acid) (PPA) were studied. Radiochemical yield of phosphonic acids labeled with 188Re, is not less than 95%, the radiochemical impurities do not exceed 5.0%. All compounds have high stability in vivo and selectively accumulate in osseous tissue. Accumulation of the above labeled compounds in osseous tissue depends on chemical structures of phosphonic acids. The level of accumulated radioactivity in skeleton following administration of the radiopharmaceticals can be arranged in the following descending order: 188Re-PPA > 188Re-HEDP > 188Re-EDTMP > 188Re-OENTMP. All compounds are rapidly excreted from blood with minimal accumulation in soft organs and tissues. The excretion of radioactivity from the bodies is occurred through the urinary routes. In other organs and tissues - the lungs, liver, spleen and muscle tissue - the maximum values of radioactivity detected immediately after injection of the preparations, however after 1 h a significant part of the activity is eliminated from these tissues.