In vivo dynamic distribution of I-131-glucagon-like peptide-1 (7-36) amidein the rat studied by gamma camera

The in vivo distribution of glucagon-like peptide-1 (7-36) amide (GLP-1) wa s studied in a rat model using radiolabeled GLP-1 (I-131-GLP-1) depicted by a gamma-camera. The dynamic scan showed a rapid clearance from the blood c irculation after an intravenous (IV) injection of I-131-GLP-1. After 10 min , the major part of the radioactivity was accumulated in the kidneys, where as about 9% (of the blood value) was found in the brain. The pharmacokinetic study using I-125-GLP-1 demonstrated a rapid eliminatio n from plasma, with a half-life of 3.3 +/- 0.6 min, a clearance of 117 +/- 15 mL/min, and a distribution volume of 557 +/- 61 mL. The elimination half -lives for the intact I-125-GLP-1 in lungs and kidneys were determined to 3 .7 and 3.9 min, respectively. The metabolite GLP-1 (9-36) amide was followe d in blood, lung, and kidney. All other organs assumed to contain low molec ular weight fragments of GLP-1. The present study suggest that GLP-1 and/or its labeled metabolites cross the blood-brain barrier. Also the kidney pla ys an essential role in GLP-1 elimination after an IV administration, which can be of clinical interest especially in patients with kidney insufficien cy who are treated with GLP-1. NUCL MED BIOL 26;4:413-420, 1999. (C) 1999 E lsevier Science Inc. All rights reserved.