Technetium-99m-labelling of p-Aminohippuric acid

The present paper describes the results of the investigation of labeling conditions (molar rations, concentrations of Sn(II), pH) for p-aminohippuric acid with technetium-99m. The Sn(II) - reduction method with and without the presence of calciumtrisodium salt of diethyltriaminopentaacetic acid (CaNa3DTPA) were used. The percentage of radiochemical purity of 99mTc-PAH was determined by two ITLC solvent systems (acetone and 0.9% NaCl). The TCA precipitation method for determination of the percentage of 99mTc-PAH bound to proteins (12% and 20% human serum albumin) was used. For lipophilicity measurements the method of Zoghbi et all. with n-butanol instead of l-octanol was used. The new radiopharmaceutical with molar ratio PAH:DTPA)=5:1, with great radiochemical purity (>95%), and stability after labelling, was obtained as a kit for labelling by adding of 99mTc-pertechnetate. The relatively small percentage of protein binding, which corresponds to the same quantity for 131I-IOH, and hydrophilic character of 99mTc-PAH complex point to its urinary route of elimination. (author)