Technetium 99m-pyridoxylideneglutamate: a new hepatobiliary radiopharmaceutical. I. Experimental aspects

The labeling of pyridoxal and the pyridoxylidene derivative of glutamic acid with 99mTc has been achieved by a simple autoclaving procedure. Technetium-99-m-pyridoxylideneglutamate (99mTc-PG) shows marked biliary excretion with accumulation of radioactivity in the gallbladder and intestines of experimental animals. This compound has been extensively investigated with a view to its application in the diagnosis of biliary disorders in man by scintigraphy. Both scintigraphic and quantitative distribution studies showed that 99mTc-PG passed rapidly through the mouse liver with progressive accumulation in the gallbladder, allowing visualization of this organ within 10 min of injection. In 30 min over 40% of the injected dose was excreted into the intestine with an equivalent amount appearing in the urine; however, renal activity remained low. Scintigraphic studies in dogs showed results similar to those obtained in mice. Studies of the toxicity in three animal species indicated a wide margin of safety for 99mTc-PG in the dose proposed for diagnostic purposes in humans.