Introduced by A. L. Sellers)There is need for a rapid and non-traumatic method for assessing individual kidney function. Use of labeled compounds and external radioactivity measurements over the kidneys appear quite adequate for the purpose. After injection, uptake and clearance by each kidney are measured by means of radioactivity, producing a printed record by use of appropriate instrumentation ( 1 ) . However, the methold used previously was complicated because the diethanolamine salt of 1131 labeled 3,5-diiodo-4-pyridone-N-acetic acid (Diodrast) was not kidney-specific and because of its hepatic uptake, required careful placement of the probes ( 2 ) . In addition, labeled analogs of sodium 3,5-diacetamido-2, 4,6-triiodobenzoate (Hypaque) , methyl-glucamine 3 , 5 -diace tamido-2,4,6-triiodobenzoa te (Renografin) , sodium 3-acetamido-2,4,6-triiodobenzoate (Urokon) , and sodium 3,5dipropionylamino-2,4,6-triiodobenzoate ( Miokon), all have the disadvantage oif being cleared slowly by the kidneys, prolonging test time to 15-25 minutes. Although they are essentially noit picked up by the liver, they differentiate less clearly the function of the individual kidneys. Theoretical considerations indicated that sodium o-idohippurate (Hippuran) had the desired characteristics folr comparing separate kidney function, namely rapid and complete removal frolm the blood by the kidneys only. This compound containing I*"* was then prepared by the 2 methods described and proved quite satisfactory for the purpose.Methods. Hippuran containing was prepared by 2 methods of exchange. In Method I , ca. 20 mc was released from N a P solution (Oak Ridge) by 0.33 ml 0.01 M KI, 0.1 ml M NaN02 and 0.2 ml 2.5 Ril:HCI and the iodine shaken out with 2 ml K l $ . The shakeout wits repeated with the same quantities of reagents but no IJ;{l. The combined CC14 solutions of were washed by shaking with 2 ml H20, then extracted with 0.5 ml H20 plus 0.6 ml 0.1 bf NaOH followed by 0.5 ml H20 plus 0.2 ml 0.02 M NaOH.The N a F solutions were added to 363 mg Hippuran dissolved in 2 ml H20 in 10 ml serum vial and adjusted to pH 6 with 0.1 M HCl and pH paper. The vial was closed with rubber stopper covered on underside with Saran film, sealed with aluminum seal and heated 2 hours in boiling water. The contents were transferred tc 201 ml beaker and evaporated to dryness, redissolved in 1 ml boiling H20 and transferred to 1 2 ml centrifuge tube. The o-iodohippuric acid was then precipitated with 0.6 ml (1 + 9) HCI, centrifuged 2500 rpm/lO min., the supernate removed, the precipitate dissolved in ca. 4.5 ml boiling H20, 1 mg K I in 0.1 ml H20 added and solution cooled in ice water and centrifuged. The precipitate was transferred using a minimum amount of supernate to a small sintered glass filter: washed with small polrtions of ice-cold saturated solutioin of non-radioactive o-iodohippuric acid and dried to constant weight a t 100". The yield was 55% of the weight of Hippuran taken and specific activity 49 pc/mg. The m.p. was 173.5" (corr.), which differed fr...
