Disposition of Recombinant Human Interleukin-2 (S-6820) (II) : Studies using ¹²⁵I-labeled S-6820 in Rats

Abstract

The distribution, excretion and metabolism of recombinant human interleukin-2 (S-6820) were studied using ¹²⁵I-labeled compound (¹²⁵I-S-6820)
1. At 5min after intravenous injection of ¹²⁵I-S-6820 to male and female rats, high radioactivity was observed in the kidney. Radioactivities in the other organs were lower than the serum level. Results obtained by whole-body autoradiography showed that high concentrations of radioactivity were found in the cortex renis.
2. At 5min after intravenous injection of ¹²⁵I-S-6820 to 20-th day pregnant rats, no radioactivities were detected in the amniotic fluid and fetus.
3. Within 24hr after intravenous injection of ¹²⁵I-S-6820, 78% and 1 % of administered radioactivity were excreted in the urine and feces, respectively. However, 98% of excreted radioactivity in the urine was not precipitated with trichloroacetic acid.
4. In the kidney after intravenous injection of ¹²⁵I-S-6820, a low molecular weight degradation products of ¹²⁵I-S-6820 were observed as revealed by gel filtration radio-chromatography. In addition, micro-autoradiogram of cortex renis after intravenous injection of ¹²⁵I-S-6820 showed that S-6820 was likely to be ultrafiltrated by the glomerulus and absorbed by proximal tubules. S-6820 appeared to be degraded in the kidney.