Synthesis of Radioactive Sodium 5-Acetamido-2, 4, 6-triiodo-N-methyl-isophthalamate (¹³¹I) and Its Application to External Measurement of Glomerular Filtration Rate in Rabbits

Abstract

Radioactive sodium 5-acetamido-2, 4, 6-triiodo-N-methyl-isophthalamate (¹³¹I) was synthesized by isotopic exchange reaction in acidic aqueous solution. When this compound was injected intravenously into rabbit, it was excreted very rapidly and little of it was taken up by organs except kidney. The blood clearance of the compound obtained by external counting after the single injection was exponential after a certain period of equilibrium and its rate was independent of the administered dose. Those results indicate that this substance is filtered at the glomeruli passively and the half clearance time can be considered to be a parameter of the renal glomerular filtration rate.