A BASIC STUDY OF ¹³¹I-HIPPURAN RENOGRAM

Abstract

Radioisotope renography, advocated first by C. C. Winter, has been one of the widely used routine split renal function tests. Yet, no clear analysis has been made on each Segment a, b and c of the renogram curve.
With the advent of efficient scinticamera, it became possible to obtain satisfactory scintigrams using the rapidly excreting material, such as Hippuran. And it is now possible that the renal excretion is evaluated not only on linear renograms, but also on dynamic scintigrams (scinticamera). Therefore, renograms have been interpreted in conjunction with the dynamic scintigrams obtained by the scinticamera. With such a current trend in mind, the autoradiography has been performed on the rabbit kidneys and on the mice for our basic understandings of the renograms. Optimal conditions for the satisfactory autoradiography of the rabbit kidneys were determined. The fundamentals were studied.
The best method was shown to be the followings; CMC paste was applied on the renal surface, the kidney was immersed for 20 seconds in acetone and dryice for freezing, the specimen was cut into sections in the range of 20-40μ in thickness and finally was exposed to a film by the Contact Method for two to three days (estimated dose: 100μ C).
A new method of the whole body autoradiography of the mice, developed by us, was as follows; twos films with different sensitivities (Fuji No. 200 and No. 100) were prepared. The specimen was first placed in contact with the No. 200 film for 2 to 3 days and then with the No. 100 film. By this way, the whole body distribution was shown in detail on the No. 200 film and the intrarenal distribution on the No. 100 film.
Analysis of the Segment a of the renogram curve was made by the renogram changing Time Constant and Record Paper Speed and by the autoradiogram, for each tracer, ¹³¹I-Hippuran, ¹³¹I-PVP and ¹⁸¹I-Human Serum Albumin. It revealed that the Segment a represented not only renal vascularity but also tubular function. But for about ten seconds following the tracer injection, the Segment a signified the pure vascularity.
The Segment b was considered to be a period of the tracer (¹³¹I-Hippuran) secretion from the proximal tubulus after being retained for a certain time, since the autoradiograms of the rabbits demonstrated that the tracer was found to be distributed in the renal cortex, especiahy in the proximal tubules, in 30 seconds to 60 following the injection and then it shifted to the outer medulla, especially to the distal tubules in. 3 to 4 minutes.
Then the tracer moved from the cortex to the medulla in distribution on the autoradiogram of the rabbit kidneys.
And on the whole body autoradiogram of mice, a sudden up-rise was observed in the urinary bladder. Therefore, the Segment c, which corresponded with this stage, was thought to mean prompt excretion into the urinary bladder.
Besides these findings, the Hippuran distribution in the mice, studied by the whole body autoradiography, have shown a fairly large amount, much more than anticipated, of the tracer existence in the liver in 10 seconds and in the wall of the GI tract in 15 minutes after the injection.