Comparison of renal extraction efficiencies for radioactive agents in the normal dog.

The renal extraction efficiencies for various radioactive agents were measured in normal anesthetized dogs during 1 hr after a single intravenous injection. Radioassays were made on serial blood samples drawn simultaneously from the aorta upstream from the renal arteries and from one renal vein. As a reference substance [131I]o-iodohippurate was injected concurrently in all experiments. Blood clearances from serial venous samples and urinary excretion also were measured. Extraction efficiency from whole blood was calculated as (A-V) divided by A, where A = aortic concentration and V = renal venous concentration. This ratio for commercial [131I]o-iodohippurate fell steadily from 88% at 30 sec to 50% at 1 hr. For "purified" [131I]o-iodohippurate the fall was less marked, to 61% at 1 hr. The EE ratios for all other agents were stable after the first minute. The Tc-99m complexes of DTPA, glucoheptonate, and acetylcysteine had ratios averaging 27-29%. The ratios of Tc-99m DMS and Hg-197 chlormerodrin had much lower average values of 8 and 14%, respectively. None of the newer agents approached the extraction efficiency of [131I]o-iodohippurate.

[Chemical form of the radioactive excretion products after intravenous application of 125I-orthoiodohippurate to rats (author's transl)]. / Chemische Form der radioaktiven Ausscheidungsprodukte nach intravenöser Verabreichung von 125J-Orthojodhippuran an Ratten.

100 muCi 125I-Orthoiodohippurate were injected i. v. to 2 Wistar rats. Urine and faeces were analysed by means of thin-layer chromatography and high-pressure liquid chromatography. The combined metabolic balance resulted in the following findings: Rat 1: 15% 125I-Orthoiodobenzoic acid, 66% 125I-Orthoiodohippuric acid and 12,5% 125I-iodide. Rat 2: 18,5% 125I-Orthoiodobenzoic acid, 67,5% 125I-Orthoiodohippuric acid and 10,2% 125I-iodide.

o- and M-iodohippurate binding to plasma proteins as a model drug transport mechanism.

The pharmacokinetics of two isomers, o- and m-iodohippurate, were determined in rabbits and rats and the effect of protein binding on their elimination is demonstrated. Both isomers are rapidly eliminated by transport systems in the kidney and their clearance by the kidney approaches the renal plasma flow regardless of protein binding, m-Iodohippurate is more highly bound to plasma proteins than o-iodohippurate and its rate of elimination is enhanced in comparison with o-iodohippurate. In the case of these two isomers, the binding to plasma proteins should be considered as a transport mechanism and not as a storage depot.

A computer program for automatic recording and processing of renograms.

A program is described, which performs automatic uptake, plotting and processing of radio-hippuran renograms obtained from a gamma camera, using an on-line minicomputer system. The program is written in machine language for a ND 50/50 system equipped with a PDP8-L processor, but translation for other nuclear medicine EDP system is easy. Minimum configuration requirements are: (i) 4K processor with TTY; (ii) external clock; (iii) magnetic tape transport; and (iv) 4K + 4K buffered camera interface or additional 8K of storage plus camera interface. Camera interface is computer-controlled and includes two AD-converters, a display unit for buffer storage and interest-areas selection facility. Operation starts recording 40 scintiphotographs of 30 sec each. Then, kidney uptake curves are obtained by subtraction of blood and tissue background, and diagnostic parameters, such as the initial slope, the maximum uptake point and 50% activity time, are computed. The only manual intervention required is the computer-assisted selection of interest-areas of kidneys, and blood and tissue background. Time required is 20 min for uptake of renograms and 5 min for processing and output, thus allowing routine execution of good quality renography, including hardcopy printout of both kidney uptake curves and diagnostic paramerers.

Prediction of urinary excretion of 131I-orthoiodohippurate.

A new formula is presented for the prediction of urinary excretion at approximately 35 min after injection of 131I-orthoiodohippurate, derived from a large series of normal kidney donors, before and after unilateral nephrectomy, and a few patients with diseases in which there was no evidence of urinary tract obstruction. The best formula was: Expected percent dose excretion at 35 min = 79.3[1-e--(0.004798 X ERPF)] with a standard error of estimate (Sy.x) of 5.2% dose. This value has been particularly useful in clinical practice in the calculation of an excretion index (actual/expected percent dose excretion) which separates various post-transplantation entities and various nephrourologic processes.

[Behavior of some functional parameters of acute incomplete drainage-impeded kidney in animal experiments]. / Das Verhalten einiger Funktionsparameter der akut inkomplett abflussbehinderten Niere im Tierexperiment.

The 131-hippuran clearance was determined preoperatively in 24 female Alsatian dogs. At three times (days 1, 7 and 28) after antireflux grafting operation, PAH, inulin, and 131I-hippuran clearances of the two kidneys were determined separately on both sides with a radioisotope nephrogram. There was a postoperative functional restriction of the operated or contralateral kidney at no time and for none of the clearance substances. However, there was a significant increase of the tubulosecretory partial function of both kidneys on the 1st postoperative day. The single findings of the radioisotope nephrograms of interest are discussed.

Renal handling of beta2-microglobulin in experimental renal disease.

Renal extraction and urinary excretion of 125I-labelled beta2-microglobulin was studied in rats. The effect of ischaemic renal injury, experimental pyelonephritis, and unilateral nephrectomy was investigated. The tubular secretion of o-iodohippurate (OIH) was measured for comparison. The urinary excretion was calculated as the ratio between the clearance of protein and the glomerular filtration rate. The glomerular filtration rate was estimated as clearance of polyethylene glycol (PEG 1000). The renal arteriovenous concentration difference was lower for beta2-microglobulin than for PEG 1000 IN ALL THE EXperimental groups. In unilateral renal disease the beta2-microglobulin excretion of the intact kidneys was similar to that of the diseased kidneys. A significant differences was noted only after ischaemic renal injury. The same was found for OIH. After removal of the intact kidneys the excretion of beta2-microglobulin increased about 10-fold in pyelonephritic animals and 2- to 30-fold in animals with ischaemic renal injury. One hour after unilateral nephrectomy in normal animals the ratio increased about 50 per cent. The tubular secretion of OIH did not change noticeably. It is concluded that the glomerular filtration is a main step in the intrarenal catabolism of beta2-microglobin and that its urinary excretion is considerably influenced by a reduction in the functioning kidney mass.